// Copyright 2017-2020 Parity Technologies (UK) Ltd.
// This file is part of Substrate.

// Substrate is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Substrate is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.

//! Tests for the module.

use super::*;
use mock::*;
use sp_runtime::{
	assert_eq_error_rate, traits::BadOrigin,
};
use sp_staking::offence::OffenceDetails;
use frame_support::{
	assert_ok, assert_noop, StorageMap,
	traits::{Currency, ReservableCurrency, OnInitialize},
};
use pallet_balances::Error as BalancesError;
use substrate_test_utils::assert_eq_uvec;
use crate::Store;

#[test]
fn force_unstake_works() {
	// Verifies initial conditions of mock
	ExtBuilder::default().build_and_execute(|| {
		// Account 11 is stashed and locked, and account 10 is the controller
		assert_eq!(Staking::bonded(&11), Some(10));
		// Cant transfer
		assert_noop!(
			Balances::transfer(Origin::signed(11), 1, 10),
			BalancesError::<Test, _>::LiquidityRestrictions
		);
		// Force unstake requires root.
		assert_noop!(Staking::force_unstake(Origin::signed(11), 11), BadOrigin);
		// We now force them to unstake
		assert_ok!(Staking::force_unstake(Origin::ROOT, 11));
		// No longer bonded.
		assert_eq!(Staking::bonded(&11), None);
		// Transfer works.
		assert_ok!(Balances::transfer(Origin::signed(11), 1, 10));
	});
}

#[test]
fn basic_setup_works() {
	// Verifies initial conditions of mock
	ExtBuilder::default().build_and_execute(|| {
		// Account 11 is stashed and locked, and account 10 is the controller
		assert_eq!(Staking::bonded(&11), Some(10));
		// Account 21 is stashed and locked, and account 20 is the controller
		assert_eq!(Staking::bonded(&21), Some(20));
		// Account 1 is not a stashed
		assert_eq!(Staking::bonded(&1), None);

		// Account 10 controls the stash from account 11, which is 100 * balance_factor units
		assert_eq!(
			Staking::ledger(&10),
			Some(StakingLedger { stash: 11, total: 1000, active: 1000, unlocking: vec![], claimed_rewards: vec![] })
		);
		// Account 20 controls the stash from account 21, which is 200 * balance_factor units
		assert_eq!(
			Staking::ledger(&20),
			Some(StakingLedger { stash: 21, total: 1000, active: 1000, unlocking: vec![], claimed_rewards: vec![] })
		);
		// Account 1 does not control any stash
		assert_eq!(Staking::ledger(&1), None);

		// ValidatorPrefs are default
		assert_eq_uvec!(<Validators<Test>>::iter().collect::<Vec<_>>(), vec![
			(31, ValidatorPrefs::default()),
			(21, ValidatorPrefs::default()),
			(11, ValidatorPrefs::default())
		]);

		assert_eq!(
			Staking::ledger(100),
			Some(StakingLedger { stash: 101, total: 500, active: 500, unlocking: vec![], claimed_rewards: vec![] })
		);
		assert_eq!(Staking::nominators(101).unwrap().targets, vec![11, 21]);

		assert_eq!(
			Staking::eras_stakers(Staking::active_era().unwrap().index, 11),
			Exposure {
				total: 1125,
				own: 1000,
				others: vec![ IndividualExposure { who: 101, value: 125 }]
			},
		);
		assert_eq!(
			Staking::eras_stakers(Staking::active_era().unwrap().index, 21),
			Exposure {
				total: 1375,
				own: 1000,
				others: vec![ IndividualExposure { who: 101, value: 375 }]
			},
		);

		// initial total stake = 1125 + 1375
		assert_eq!(Staking::eras_total_stake(Staking::active_era().unwrap().index), 2500);


		// The number of validators required.
		assert_eq!(Staking::validator_count(), 2);

		// Initial Era and session
		assert_eq!(Staking::active_era().unwrap().index, 0);

		// Account 10 has `balance_factor` free balance
		assert_eq!(Balances::free_balance(10), 1);
		assert_eq!(Balances::free_balance(10), 1);

		// New era is not being forced
		assert_eq!(Staking::force_era(), Forcing::NotForcing);
	});
}

#[test]
fn change_controller_works() {
	ExtBuilder::default().build_and_execute(|| {
		assert_eq!(Staking::bonded(&11), Some(10));

		assert!(Session::validators().contains(&11));
		// 10 can control 11 who is initially a validator.
		assert_ok!(Staking::chill(Origin::signed(10)));
		assert!(Session::validators().contains(&11));

		assert_ok!(Staking::set_controller(Origin::signed(11), 5));

		mock::start_era(1);

		assert_noop!(
			Staking::validate(Origin::signed(10), ValidatorPrefs::default()),
			Error::<Test>::NotController,
		);
		assert_ok!(Staking::validate(Origin::signed(5), ValidatorPrefs::default()));
	})
}

#[test]
fn rewards_should_work() {
	// should check that:
	// * rewards get recorded per session
	// * rewards get paid per Era
	// * Check that nominators are also rewarded
	ExtBuilder::default().nominate(true).build_and_execute(|| {
		let init_balance_10 = Balances::total_balance(&10);
		let init_balance_11 = Balances::total_balance(&11);
		let init_balance_20 = Balances::total_balance(&20);
		let init_balance_21 = Balances::total_balance(&21);
		let init_balance_100 = Balances::total_balance(&100);
		let init_balance_101 = Balances::total_balance(&101);

		// Check state
		Payee::<Test>::insert(11, RewardDestination::Controller);
		Payee::<Test>::insert(21, RewardDestination::Controller);
		Payee::<Test>::insert(101, RewardDestination::Controller);

		<Module<Test>>::reward_by_ids(vec![(11, 50)]);
		<Module<Test>>::reward_by_ids(vec![(11, 50)]);
		// This is the second validator of the current elected set.
		<Module<Test>>::reward_by_ids(vec![(21, 50)]);

		// Compute total payout now for whole duration as other parameter won't change
		let total_payout_0 = current_total_payout_for_duration(3 * 1000);
		assert!(total_payout_0 > 10); // Test is meaningful if reward something

		start_session(1);

		assert_eq!(Balances::total_balance(&10), init_balance_10);
		assert_eq!(Balances::total_balance(&11), init_balance_11);
		assert_eq!(Balances::total_balance(&20), init_balance_20);
		assert_eq!(Balances::total_balance(&21), init_balance_21);
		assert_eq!(Balances::total_balance(&100), init_balance_100);
		assert_eq!(Balances::total_balance(&101), init_balance_101);
		assert_eq_uvec!(Session::validators(), vec![11, 21]);
		assert_eq!(Staking::eras_reward_points(Staking::active_era().unwrap().index), EraRewardPoints {
			total: 50*3,
			individual: vec![(11, 100), (21, 50)].into_iter().collect(),
		});
		let part_for_10 = Perbill::from_rational_approximation::<u32>(1000, 1125);
		let part_for_20 = Perbill::from_rational_approximation::<u32>(1000, 1375);
		let part_for_100_from_10 = Perbill::from_rational_approximation::<u32>(125, 1125);
		let part_for_100_from_20 = Perbill::from_rational_approximation::<u32>(375, 1375);

		start_session(2);
		start_session(3);

		assert_eq!(Staking::active_era().unwrap().index, 1);
		mock::make_all_reward_payment(0);

		assert_eq_error_rate!(Balances::total_balance(&10), init_balance_10 + part_for_10 * total_payout_0*2/3, 2);
		assert_eq_error_rate!(Balances::total_balance(&11), init_balance_11, 2);
		assert_eq_error_rate!(Balances::total_balance(&20), init_balance_20 + part_for_20 * total_payout_0*1/3, 2);
		assert_eq_error_rate!(Balances::total_balance(&21), init_balance_21, 2);
		assert_eq_error_rate!(
			Balances::total_balance(&100),
			init_balance_100
				+ part_for_100_from_10 * total_payout_0 * 2/3
				+ part_for_100_from_20 * total_payout_0 * 1/3,
			2
		);
		assert_eq_error_rate!(Balances::total_balance(&101), init_balance_101, 2);

		assert_eq_uvec!(Session::validators(), vec![11, 21]);
		<Module<Test>>::reward_by_ids(vec![(11, 1)]);

		// Compute total payout now for whole duration as other parameter won't change
		let total_payout_1 = current_total_payout_for_duration(3 * 1000);
		assert!(total_payout_1 > 10); // Test is meaningful if reward something

		mock::start_era(2);
		mock::make_all_reward_payment(1);

		assert_eq_error_rate!(Balances::total_balance(&10), init_balance_10 + part_for_10 * (total_payout_0 * 2/3 + total_payout_1), 2);
		assert_eq_error_rate!(Balances::total_balance(&11), init_balance_11, 2);
		assert_eq_error_rate!(Balances::total_balance(&20), init_balance_20 + part_for_20 * total_payout_0 * 1/3, 2);
		assert_eq_error_rate!(Balances::total_balance(&21), init_balance_21, 2);
		assert_eq_error_rate!(
			Balances::total_balance(&100),
			init_balance_100
				+ part_for_100_from_10 * (total_payout_0 * 2/3 + total_payout_1)
				+ part_for_100_from_20 * total_payout_0 * 1/3,
			2
		);
		assert_eq_error_rate!(Balances::total_balance(&101), init_balance_101, 2);
	});
}

#[test]
fn staking_should_work() {
	// should test:
	// * new validators can be added to the default set
	// * new ones will be chosen per era
	// * either one can unlock the stash and back-down from being a validator via `chill`ing.
	ExtBuilder::default()
		.nominate(false)
		.fair(false) // to give 20 more staked value
		.build()
		.execute_with(|| {
			// --- Block 1:
			start_session(1);

			// remember + compare this along with the test.
			assert_eq_uvec!(validator_controllers(), vec![20, 10]);

			// put some money in account that we'll use.
			for i in 1..5 { let _ = Balances::make_free_balance_be(&i, 2000); }

			// --- Block 2:
			start_session(2);
			// add a new candidate for being a validator. account 3 controlled by 4.
			assert_ok!(Staking::bond(Origin::signed(3), 4, 1500, RewardDestination::Controller));
			assert_ok!(Staking::validate(Origin::signed(4), ValidatorPrefs::default()));

			// No effects will be seen so far.
			assert_eq_uvec!(validator_controllers(), vec![20, 10]);

			// --- Block 3:
			start_session(3);

			// No effects will be seen so far. Era has not been yet triggered.
			assert_eq_uvec!(validator_controllers(), vec![20, 10]);


			// --- Block 4: the validators will now be queued.
			start_session(4);
			assert_eq!(Staking::active_era().unwrap().index, 1);

			// --- Block 5: the validators are still in queue.
			start_session(5);

			// --- Block 6: the validators will now be changed.
			start_session(6);

			assert_eq_uvec!(validator_controllers(), vec![20, 4]);
			// --- Block 6: Unstake 4 as a validator, freeing up the balance stashed in 3
			// 4 will chill
			Staking::chill(Origin::signed(4)).unwrap();

			// --- Block 7: nothing. 4 is still there.
			start_session(7);
			assert_eq_uvec!(validator_controllers(), vec![20, 4]);

			// --- Block 8:
			start_session(8);

			// --- Block 9: 4 will not be a validator.
			start_session(9);
			assert_eq_uvec!(validator_controllers(), vec![20, 10]);

			// Note: the stashed value of 4 is still lock
			assert_eq!(
				Staking::ledger(&4),
				Some(StakingLedger {
					stash: 3,
					total: 1500,
					active: 1500,
					unlocking: vec![],
					claimed_rewards: vec![0],
				})
			);
			// e.g. it cannot spend more than 500 that it has free from the total 2000
			assert_noop!(
				Balances::reserve(&3, 501),
				BalancesError::<Test, _>::LiquidityRestrictions
			);
			assert_ok!(Balances::reserve(&3, 409));
		});
}

#[test]
fn less_than_needed_candidates_works() {
	ExtBuilder::default()
		.minimum_validator_count(1)
		.validator_count(4)
		.nominate(false)
		.num_validators(3)
		.build()
		.execute_with(|| {
			assert_eq!(Staking::validator_count(), 4);
			assert_eq!(Staking::minimum_validator_count(), 1);
			assert_eq_uvec!(validator_controllers(), vec![30, 20, 10]);

			mock::start_era(1);

			// Previous set is selected. NO election algorithm is even executed.
			assert_eq_uvec!(validator_controllers(), vec![30, 20, 10]);

			// But the exposure is updated in a simple way. No external votes exists.
			// This is purely self-vote.
			assert!(
				ErasStakers::<Test>::iter_prefix(Staking::active_era().unwrap().index)
					.all(|exposure| exposure.others.is_empty())
			);
		});
}

#[test]
fn no_candidate_emergency_condition() {
	ExtBuilder::default()
		.minimum_validator_count(1)
		.validator_count(15)
		.num_validators(4)
		.validator_pool(true)
		.nominate(false)
		.build()
		.execute_with(|| {
			// initial validators
			assert_eq_uvec!(validator_controllers(), vec![10, 20, 30, 40]);
			let prefs = ValidatorPrefs { commission: Perbill::one() };
			<Staking as crate::Store>::Validators::insert(11, prefs.clone());

			// set the minimum validator count.
			<Staking as crate::Store>::MinimumValidatorCount::put(10);

			// try to chill
			let _ = Staking::chill(Origin::signed(10));

			// trigger era
			mock::start_era(1);

			// Previous ones are elected. chill is invalidates. TODO: #2494
			assert_eq_uvec!(validator_controllers(), vec![10, 20, 30, 40]);
			// Though the validator preferences has been removed.
			assert!(Staking::validators(11) != prefs);
		});
}

#[test]
fn nominating_and_rewards_should_work() {
	// PHRAGMEN OUTPUT: running this test with the reference impl gives:
	//
	// Sequential Phragmén gives
	// 10  is elected with stake  2200.0 and score  0.0003333333333333333
	// 20  is elected with stake  1800.0 and score  0.0005555555555555556

	// 10  has load  0.0003333333333333333 and supported
	// 10  with stake  1000.0
	// 20  has load  0.0005555555555555556 and supported
	// 20  with stake  1000.0
	// 30  has load  0 and supported
	// 30  with stake  0
	// 40  has load  0 and supported
	// 40  with stake  0
	// 2  has load  0.0005555555555555556 and supported
	// 10  with stake  600.0 20  with stake  400.0 30  with stake  0.0
	// 4  has load  0.0005555555555555556 and supported
	// 10  with stake  600.0 20  with stake  400.0 40  with stake  0.0

	// Sequential Phragmén with post processing gives
	// 10  is elected with stake  2000.0 and score  0.0003333333333333333
	// 20  is elected with stake  2000.0 and score  0.0005555555555555556

	// 10  has load  0.0003333333333333333 and supported
	// 10  with stake  1000.0
	// 20  has load  0.0005555555555555556 and supported
	// 20  with stake  1000.0
	// 30  has load  0 and supported
	// 30  with stake  0
	// 40  has load  0 and supported
	// 40  with stake  0
	// 2  has load  0.0005555555555555556 and supported
	// 10  with stake  400.0 20  with stake  600.0 30  with stake  0
	// 4  has load  0.0005555555555555556 and supported
	// 10  with stake  600.0 20  with stake  400.0 40  with stake  0.0
	ExtBuilder::default()
		.nominate(false)
		.validator_pool(true)
		.build()
		.execute_with(|| {
			// initial validators -- everyone is actually even.
			assert_eq_uvec!(validator_controllers(), vec![40, 30]);

			// Set payee to controller
			assert_ok!(Staking::set_payee(Origin::signed(10), RewardDestination::Controller));
			assert_ok!(Staking::set_payee(Origin::signed(20), RewardDestination::Controller));
			assert_ok!(Staking::set_payee(Origin::signed(30), RewardDestination::Controller));
			assert_ok!(Staking::set_payee(Origin::signed(40), RewardDestination::Controller));

			// give the man some money
			let initial_balance = 1000;
			for i in [1, 2, 3, 4, 5, 10, 11, 20, 21].iter() {
				let _ = Balances::make_free_balance_be(i, initial_balance);
			}

			// bond two account pairs and state interest in nomination.
			// 2 will nominate for 10, 20, 30
			assert_ok!(Staking::bond(Origin::signed(1), 2, 1000, RewardDestination::Controller));
			assert_ok!(Staking::nominate(Origin::signed(2), vec![11, 21, 31]));
			// 4 will nominate for 10, 20, 40
			assert_ok!(Staking::bond(Origin::signed(3), 4, 1000, RewardDestination::Controller));
			assert_ok!(Staking::nominate(Origin::signed(4), vec![11, 21, 41]));

			// the total reward for era 0
			let total_payout_0 = current_total_payout_for_duration(3000);
			assert!(total_payout_0 > 100); // Test is meaningful if reward something
			<Module<Test>>::reward_by_ids(vec![(41, 1)]);
			<Module<Test>>::reward_by_ids(vec![(31, 1)]);

			mock::start_era(1);

			// 10 and 20 have more votes, they will be chosen by phragmen.
			assert_eq_uvec!(validator_controllers(), vec![20, 10]);

			// OLD validators must have already received some rewards.
			mock::make_all_reward_payment(0);
			assert_eq!(Balances::total_balance(&40), 1 + total_payout_0 / 2);
			assert_eq!(Balances::total_balance(&30), 1 + total_payout_0 / 2);

			// ------ check the staked value of all parties.

			// 30 and 40 are not chosen anymore
			assert_eq!(ErasStakers::<Test>::iter_prefix(Staking::active_era().unwrap().index).count(), 2);
			assert_eq!(
				Staking::eras_stakers(Staking::active_era().unwrap().index, 11),
				Exposure {
					total: 1000 + 800,
					own: 1000,
					others: vec![
						IndividualExposure { who: 3, value: 400 },
						IndividualExposure { who: 1, value: 400 },
					]
				},
			);
			assert_eq!(
				Staking::eras_stakers(Staking::active_era().unwrap().index, 21),
				Exposure {
					total: 1000 + 1200,
					own: 1000,
					others: vec![
						IndividualExposure { who: 3, value: 600 },
						IndividualExposure { who: 1, value: 600 },
					]
				},
			);

			// the total reward for era 1
			let total_payout_1 = current_total_payout_for_duration(3000);
			assert!(total_payout_1 > 100); // Test is meaningful if reward something
			<Module<Test>>::reward_by_ids(vec![(21, 2)]);
			<Module<Test>>::reward_by_ids(vec![(11, 1)]);

			mock::start_era(2);

			// nothing else will happen, era ends and rewards are paid again,
			// it is expected that nominators will also be paid. See below

			mock::make_all_reward_payment(1);
			let payout_for_10 = total_payout_1 / 3;
			let payout_for_20 = 2 * total_payout_1 / 3;
			// Nominator 2: has [400/1800 ~ 2/9 from 10] + [600/2200 ~ 3/11 from 20]'s reward. ==> 2/9 + 3/11
			assert_eq_error_rate!(
				Balances::total_balance(&2),
				initial_balance + (2 * payout_for_10 / 9 + 3 * payout_for_20 / 11),
				1,
			);
			// Nominator 4: has [400/1800 ~ 2/9 from 10] + [600/2200 ~ 3/11 from 20]'s reward. ==> 2/9 + 3/11
			assert_eq_error_rate!(
				Balances::total_balance(&4),
				initial_balance + (2 * payout_for_10 / 9 + 3 * payout_for_20 / 11),
				1,
			);

			// Validator 10: got 800 / 1800 external stake => 8/18 =? 4/9 => Validator's share = 5/9
			assert_eq_error_rate!(
				Balances::total_balance(&10),
				initial_balance + 5 * payout_for_10 / 9,
				1,
			);
			// Validator 20: got 1200 / 2200 external stake => 12/22 =? 6/11 => Validator's share = 5/11
			assert_eq_error_rate!(
				Balances::total_balance(&20),
				initial_balance + 5 * payout_for_20 / 11,
				1,
			);
		});
}

#[test]
fn nominators_also_get_slashed() {
	// A nominator should be slashed if the validator they nominated is slashed
	// Here is the breakdown of roles:
	// 10 - is the controller of 11
	// 11 - is the stash.
	// 2 - is the nominator of 20, 10
	ExtBuilder::default().nominate(false).build_and_execute(|| {
		assert_eq!(Staking::validator_count(), 2);

		// Set payee to controller
		assert_ok!(Staking::set_payee(Origin::signed(10), RewardDestination::Controller));

		// give the man some money.
		let initial_balance = 1000;
		for i in [1, 2, 3, 10].iter() {
			let _ = Balances::make_free_balance_be(i, initial_balance);
		}

		// 2 will nominate for 10, 20
		let nominator_stake = 500;
		assert_ok!(Staking::bond(Origin::signed(1), 2, nominator_stake, RewardDestination::default()));
		assert_ok!(Staking::nominate(Origin::signed(2), vec![20, 10]));

		let total_payout = current_total_payout_for_duration(3000);
		assert!(total_payout > 100); // Test is meaningful if reward something
		<Module<Test>>::reward_by_ids(vec![(11, 1)]);

		// new era, pay rewards,
		mock::start_era(1);

		// Nominator stash didn't collect any.
		assert_eq!(Balances::total_balance(&2), initial_balance);

		// 10 goes offline
		on_offence_now(
			&[OffenceDetails {
				offender: (
					11,
					Staking::eras_stakers(Staking::active_era().unwrap().index, 11),
				),
				reporters: vec![],
			}],
			&[Perbill::from_percent(5)],
		);
		let expo = Staking::eras_stakers(Staking::active_era().unwrap().index, 11);
		let slash_value = 50;
		let total_slash = expo.total.min(slash_value);
		let validator_slash = expo.own.min(total_slash);
		let nominator_slash = nominator_stake.min(total_slash - validator_slash);

		// initial + first era reward + slash
		assert_eq!(Balances::total_balance(&11), initial_balance - validator_slash);
		assert_eq!(Balances::total_balance(&2), initial_balance - nominator_slash);

		// Because slashing happened.
		assert!(is_disabled(10));
	});
}

#[test]
fn double_staking_should_fail() {
	// should test (in the same order):
	// * an account already bonded as stash cannot be be stashed again.
	// * an account already bonded as stash cannot nominate.
	// * an account already bonded as controller can nominate.
	ExtBuilder::default().build_and_execute(|| {
		let arbitrary_value = 5;
		// 2 = controller, 1 stashed => ok
		assert_ok!(
			Staking::bond(Origin::signed(1), 2, arbitrary_value,
			RewardDestination::default())
		);
		// 4 = not used so far, 1 stashed => not allowed.
		assert_noop!(
			Staking::bond(Origin::signed(1), 4, arbitrary_value,
			RewardDestination::default()), Error::<Test>::AlreadyBonded,
		);
		// 1 = stashed => attempting to nominate should fail.
		assert_noop!(Staking::nominate(Origin::signed(1), vec![1]), Error::<Test>::NotController);
		// 2 = controller  => nominating should work.
		assert_ok!(Staking::nominate(Origin::signed(2), vec![1]));
	});
}

#[test]
fn double_controlling_should_fail() {
	// should test (in the same order):
	// * an account already bonded as controller CANNOT be reused as the controller of another account.
	ExtBuilder::default().build_and_execute(|| {
		let arbitrary_value = 5;
		// 2 = controller, 1 stashed => ok
		assert_ok!(Staking::bond(
			Origin::signed(1),
			2,
			arbitrary_value,
			RewardDestination::default(),
		));
		// 2 = controller, 3 stashed (Note that 2 is reused.) => no-op
		assert_noop!(
			Staking::bond(Origin::signed(3), 2, arbitrary_value, RewardDestination::default()),
			Error::<Test>::AlreadyPaired,
		);
	});
}

#[test]
fn session_and_eras_work() {
	ExtBuilder::default().build_and_execute(|| {
		assert_eq!(Staking::active_era().unwrap().index, 0);
		assert_eq!(Session::current_index(), 0);

		// Session 1: No change.
		start_session(1);
		assert_eq!(Session::current_index(), 1);
		assert_eq!(Staking::active_era().unwrap().index, 0);

		// Session 2: No change.
		start_session(2);
		assert_eq!(Session::current_index(), 2);
		assert_eq!(Staking::active_era().unwrap().index, 0);

		// Session 3: Era increment.
		start_session(3);
		assert_eq!(Session::current_index(), 3);
		assert_eq!(Staking::active_era().unwrap().index, 1);

		// Session 4: No change.
		start_session(4);
		assert_eq!(Session::current_index(), 4);
		assert_eq!(Staking::active_era().unwrap().index, 1);

		// Session 5: No change.
		start_session(5);
		assert_eq!(Session::current_index(), 5);
		assert_eq!(Staking::active_era().unwrap().index, 1);

		// Session 6: Era increment.
		start_session(6);
		assert_eq!(Session::current_index(), 6);
		assert_eq!(Staking::active_era().unwrap().index, 2);
	});
}

#[test]
fn forcing_new_era_works() {
	ExtBuilder::default().build_and_execute(|| {
		// normal flow of session.
		assert_eq!(Staking::active_era().unwrap().index, 0);
		start_session(0);
		assert_eq!(Staking::active_era().unwrap().index, 0);
		start_session(1);
		assert_eq!(Staking::active_era().unwrap().index, 0);
		start_session(2);
		assert_eq!(Staking::active_era().unwrap().index, 0);
		start_session(3);
		assert_eq!(Staking::active_era().unwrap().index, 1);

		// no era change.
		ForceEra::put(Forcing::ForceNone);
		start_session(4);
		assert_eq!(Staking::active_era().unwrap().index, 1);
		start_session(5);
		assert_eq!(Staking::active_era().unwrap().index, 1);
		start_session(6);
		assert_eq!(Staking::active_era().unwrap().index, 1);
		start_session(7);
		assert_eq!(Staking::active_era().unwrap().index, 1);

		// back to normal.
		// this immediately starts a new session.
		ForceEra::put(Forcing::NotForcing);
		start_session(8);
		assert_eq!(Staking::active_era().unwrap().index, 1); // There is one session delay
		start_session(9);
		assert_eq!(Staking::active_era().unwrap().index, 2);

		// forceful change
		ForceEra::put(Forcing::ForceAlways);
		start_session(10);
		assert_eq!(Staking::active_era().unwrap().index, 2); // There is one session delay
		start_session(11);
		assert_eq!(Staking::active_era().unwrap().index, 3);
		start_session(12);
		assert_eq!(Staking::active_era().unwrap().index, 4);

		// just one forceful change
		ForceEra::put(Forcing::ForceNew);
		start_session(13);
		assert_eq!(Staking::active_era().unwrap().index, 5);
		assert_eq!(ForceEra::get(), Forcing::NotForcing);
		start_session(14);
		assert_eq!(Staking::active_era().unwrap().index, 6);
		start_session(15);
		assert_eq!(Staking::active_era().unwrap().index, 6);

	});
}

#[test]
fn cannot_transfer_staked_balance() {
	// Tests that a stash account cannot transfer funds
	ExtBuilder::default().nominate(false).build_and_execute(|| {
		// Confirm account 11 is stashed
		assert_eq!(Staking::bonded(&11), Some(10));
		// Confirm account 11 has some free balance
		assert_eq!(Balances::free_balance(11), 1000);
		// Confirm account 11 (via controller 10) is totally staked
		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 11).total, 1000);
		// Confirm account 11 cannot transfer as a result
		assert_noop!(
			Balances::transfer(Origin::signed(11), 20, 1),
			BalancesError::<Test, _>::LiquidityRestrictions
		);

		// Give account 11 extra free balance
		let _ = Balances::make_free_balance_be(&11, 10000);
		// Confirm that account 11 can now transfer some balance
		assert_ok!(Balances::transfer(Origin::signed(11), 20, 1));
	});
}

#[test]
fn cannot_transfer_staked_balance_2() {
	// Tests that a stash account cannot transfer funds
	// Same test as above but with 20, and more accurate.
	// 21 has 2000 free balance but 1000 at stake
	ExtBuilder::default().nominate(false).fair(true).build_and_execute(|| {
		// Confirm account 21 is stashed
		assert_eq!(Staking::bonded(&21), Some(20));
		// Confirm account 21 has some free balance
		assert_eq!(Balances::free_balance(21), 2000);
		// Confirm account 21 (via controller 20) is totally staked
		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 21).total, 1000);
		// Confirm account 21 can transfer at most 1000
		assert_noop!(
			Balances::transfer(Origin::signed(21), 20, 1001),
			BalancesError::<Test, _>::LiquidityRestrictions
		);
		assert_ok!(Balances::transfer(Origin::signed(21), 20, 1000));
	});
}

#[test]
fn cannot_reserve_staked_balance() {
	// Checks that a bonded account cannot reserve balance from free balance
	ExtBuilder::default().build_and_execute(|| {
		// Confirm account 11 is stashed
		assert_eq!(Staking::bonded(&11), Some(10));
		// Confirm account 11 has some free balance
		assert_eq!(Balances::free_balance(11), 1000);
		// Confirm account 11 (via controller 10) is totally staked
		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 11).own, 1000);
		// Confirm account 11 cannot transfer as a result
		assert_noop!(
			Balances::reserve(&11, 1),
			BalancesError::<Test, _>::LiquidityRestrictions
		);

		// Give account 11 extra free balance
		let _ = Balances::make_free_balance_be(&11, 10000);
		// Confirm account 11 can now reserve balance
		assert_ok!(Balances::reserve(&11, 1));
	});
}

#[test]
fn reward_destination_works() {
	// Rewards go to the correct destination as determined in Payee
	ExtBuilder::default().nominate(false).build_and_execute(|| {
		// Check that account 11 is a validator
		assert!(Session::validators().contains(&11));
		// Check the balance of the validator account
		assert_eq!(Balances::free_balance(10), 1);
		// Check the balance of the stash account
		assert_eq!(Balances::free_balance(11), 1000);
		// Check how much is at stake
		assert_eq!(Staking::ledger(&10), Some(StakingLedger {
			stash: 11,
			total: 1000,
			active: 1000,
			unlocking: vec![],
			claimed_rewards: vec![],
		}));

		// Compute total payout now for whole duration as other parameter won't change
		let total_payout_0 = current_total_payout_for_duration(3000);
		assert!(total_payout_0 > 100); // Test is meaningful if reward something
		<Module<Test>>::reward_by_ids(vec![(11, 1)]);

		mock::start_era(1);
		mock::make_all_reward_payment(0);

		// Check that RewardDestination is Staked (default)
		assert_eq!(Staking::payee(&11), RewardDestination::Staked);
		// Check that reward went to the stash account of validator
		assert_eq!(Balances::free_balance(11), 1000 + total_payout_0);
		// Check that amount at stake increased accordingly
		assert_eq!(Staking::ledger(&10), Some(StakingLedger {
			stash: 11,
			total: 1000 + total_payout_0,
			active: 1000 + total_payout_0,
			unlocking: vec![],
			claimed_rewards: vec![0],
		}));

		//Change RewardDestination to Stash
		<Payee<Test>>::insert(&11, RewardDestination::Stash);

		// Compute total payout now for whole duration as other parameter won't change
		let total_payout_1 = current_total_payout_for_duration(3000);
		assert!(total_payout_1 > 100); // Test is meaningful if reward something
		<Module<Test>>::reward_by_ids(vec![(11, 1)]);

		mock::start_era(2);
		mock::make_all_reward_payment(1);

		// Check that RewardDestination is Stash
		assert_eq!(Staking::payee(&11), RewardDestination::Stash);
		// Check that reward went to the stash account
		assert_eq!(Balances::free_balance(11), 1000 + total_payout_0 + total_payout_1);
		// Record this value
		let recorded_stash_balance = 1000 + total_payout_0 + total_payout_1;
		// Check that amount at stake is NOT increased
		assert_eq!(Staking::ledger(&10), Some(StakingLedger {
			stash: 11,
			total: 1000 + total_payout_0,
			active: 1000 + total_payout_0,
			unlocking: vec![],
			claimed_rewards: vec![0,1],
		}));

		// Change RewardDestination to Controller
		<Payee<Test>>::insert(&11, RewardDestination::Controller);

		// Check controller balance
		assert_eq!(Balances::free_balance(10), 1);

		// Compute total payout now for whole duration as other parameter won't change
		let total_payout_2 = current_total_payout_for_duration(3000);
		assert!(total_payout_2 > 100); // Test is meaningful if reward something
		<Module<Test>>::reward_by_ids(vec![(11, 1)]);

		mock::start_era(3);
		mock::make_all_reward_payment(2);

		// Check that RewardDestination is Controller
		assert_eq!(Staking::payee(&11), RewardDestination::Controller);
		// Check that reward went to the controller account
		assert_eq!(Balances::free_balance(10), 1 + total_payout_2);
		// Check that amount at stake is NOT increased
		assert_eq!(Staking::ledger(&10), Some(StakingLedger {
			stash: 11,
			total: 1000 + total_payout_0,
			active: 1000 + total_payout_0,
			unlocking: vec![],
			claimed_rewards: vec![0,1,2],
		}));
		// Check that amount in staked account is NOT increased.
		assert_eq!(Balances::free_balance(11), recorded_stash_balance);
	});
}

#[test]
fn validator_payment_prefs_work() {
	// Test that validator preferences are correctly honored
	// Note: unstake threshold is being directly tested in slashing tests.
	// This test will focus on validator payment.
	ExtBuilder::default().build_and_execute(|| {
		let commission = Perbill::from_percent(40);
		<Validators<Test>>::insert(&11, ValidatorPrefs {
			commission: commission.clone(),
		});

		// Reward controller so staked ratio doesn't change.
		<Payee<Test>>::insert(&11, RewardDestination::Controller);
		<Payee<Test>>::insert(&101, RewardDestination::Controller);

		mock::start_era(1);
		mock::make_all_reward_payment(0);

		let balance_era_1_10 = Balances::total_balance(&10);
		let balance_era_1_100 = Balances::total_balance(&100);

		// Compute total payout now for whole duration as other parameter won't change
		let total_payout_1 = current_total_payout_for_duration(3000);
		assert!(total_payout_1 > 100); // Test is meaningful if reward something
		let exposure_1 = Staking::eras_stakers(Staking::active_era().unwrap().index, 11);
		<Module<Test>>::reward_by_ids(vec![(11, 1)]);

		mock::start_era(2);
		mock::make_all_reward_payment(1);

		let taken_cut = commission * total_payout_1;
		let shared_cut = total_payout_1 - taken_cut;
		let reward_of_10 = shared_cut * exposure_1.own / exposure_1.total + taken_cut;
		let reward_of_100 = shared_cut * exposure_1.others[0].value / exposure_1.total;
		assert_eq_error_rate!(Balances::total_balance(&10), balance_era_1_10 + reward_of_10, 2);
		assert_eq_error_rate!(Balances::total_balance(&100), balance_era_1_100 + reward_of_100, 2);
	});

}

#[test]
fn bond_extra_works() {
	// Tests that extra `free_balance` in the stash can be added to stake
	// NOTE: this tests only verifies `StakingLedger` for correct updates
	// See `bond_extra_and_withdraw_unbonded_works` for more details and updates on `Exposure`.
	ExtBuilder::default().build_and_execute(|| {
		// Check that account 10 is a validator
		assert!(<Validators<Test>>::contains_key(11));
		// Check that account 10 is bonded to account 11
		assert_eq!(Staking::bonded(&11), Some(10));
		// Check how much is at stake
		assert_eq!(Staking::ledger(&10), Some(StakingLedger {
			stash: 11,
			total: 1000,
			active: 1000,
			unlocking: vec![],
			claimed_rewards: vec![],
		}));

		// Give account 11 some large free balance greater than total
		let _ = Balances::make_free_balance_be(&11, 1000000);

		// Call the bond_extra function from controller, add only 100
		assert_ok!(Staking::bond_extra(Origin::signed(11), 100));
		// There should be 100 more `total` and `active` in the ledger
		assert_eq!(Staking::ledger(&10), Some(StakingLedger {
			stash: 11,
			total: 1000 + 100,
			active: 1000 + 100,
			unlocking: vec![],
			claimed_rewards: vec![],
		}));

		// Call the bond_extra function with a large number, should handle it
		assert_ok!(Staking::bond_extra(Origin::signed(11), Balance::max_value()));
		// The full amount of the funds should now be in the total and active
		assert_eq!(Staking::ledger(&10), Some(StakingLedger {
			stash: 11,
			total: 1000000,
			active: 1000000,
			unlocking: vec![],
			claimed_rewards: vec![],
		}));
	});
}

#[test]
fn bond_extra_and_withdraw_unbonded_works() {
	// * Should test
	// * Given an account being bonded [and chosen as a validator](not mandatory)
	// * It can add extra funds to the bonded account.
	// * it can unbond a portion of its funds from the stash account.
	// * Once the unbonding period is done, it can actually take the funds out of the stash.
	ExtBuilder::default().nominate(false).build_and_execute(|| {
		// Set payee to controller. avoids confusion
		assert_ok!(Staking::set_payee(Origin::signed(10), RewardDestination::Controller));

		// Give account 11 some large free balance greater than total
		let _ = Balances::make_free_balance_be(&11, 1000000);

		// Initial config should be correct
		assert_eq!(Staking::active_era().unwrap().index, 0);
		assert_eq!(Session::current_index(), 0);

		// check the balance of a validator accounts.
		assert_eq!(Balances::total_balance(&10), 1);

		// confirm that 10 is a normal validator and gets paid at the end of the era.
		mock::start_era(1);

		// Initial state of 10
		assert_eq!(Staking::ledger(&10), Some(StakingLedger {
			stash: 11,
			total: 1000,
			active: 1000,
			unlocking: vec![],
			claimed_rewards: vec![],
		}));
		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 11), Exposure { total: 1000, own: 1000, others: vec![] });

		// deposit the extra 100 units
		Staking::bond_extra(Origin::signed(11), 100).unwrap();

		assert_eq!(Staking::ledger(&10), Some(StakingLedger {
			stash: 11,
			total: 1000 + 100,
			active: 1000 + 100,
			unlocking: vec![],
			claimed_rewards: vec![],
		}));
		// Exposure is a snapshot! only updated after the next era update.
		assert_ne!(Staking::eras_stakers(Staking::active_era().unwrap().index, 11), Exposure { total: 1000 + 100, own: 1000 + 100, others: vec![] });

		// trigger next era.
		mock::start_era(2);
		assert_eq!(Staking::active_era().unwrap().index, 2);

		// ledger should be the same.
		assert_eq!(Staking::ledger(&10), Some(StakingLedger {
			stash: 11,
			total: 1000 + 100,
			active: 1000 + 100,
			unlocking: vec![],
			claimed_rewards: vec![],
		}));
		// Exposure is now updated.
		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 11), Exposure { total: 1000 + 100, own: 1000 + 100, others: vec![] });

		// Unbond almost all of the funds in stash.
		Staking::unbond(Origin::signed(10), 1000).unwrap();
		assert_eq!(Staking::ledger(&10), Some(StakingLedger {
			stash: 11, total: 1000 + 100, active: 100, unlocking: vec![UnlockChunk{ value: 1000, era: 2 + 3}], claimed_rewards: vec![] })
		);

		// Attempting to free the balances now will fail. 2 eras need to pass.
		Staking::withdraw_unbonded(Origin::signed(10)).unwrap();
		assert_eq!(Staking::ledger(&10), Some(StakingLedger {
			stash: 11, total: 1000 + 100, active: 100, unlocking: vec![UnlockChunk{ value: 1000, era: 2 + 3}], claimed_rewards: vec![] }));

		// trigger next era.
		mock::start_era(3);

		// nothing yet
		Staking::withdraw_unbonded(Origin::signed(10)).unwrap();
		assert_eq!(Staking::ledger(&10), Some(StakingLedger {
			stash: 11, total: 1000 + 100, active: 100, unlocking: vec![UnlockChunk{ value: 1000, era: 2 + 3}], claimed_rewards: vec![] }));

		// trigger next era.
		mock::start_era(5);

		Staking::withdraw_unbonded(Origin::signed(10)).unwrap();
		// Now the value is free and the staking ledger is updated.
		assert_eq!(Staking::ledger(&10), Some(StakingLedger {
			stash: 11, total: 100, active: 100, unlocking: vec![], claimed_rewards: vec![] }));
	})
}

#[test]
fn too_many_unbond_calls_should_not_work() {
	ExtBuilder::default().build_and_execute(|| {
		// locked at era 0 until 3
		for _ in 0..MAX_UNLOCKING_CHUNKS-1 {
			assert_ok!(Staking::unbond(Origin::signed(10), 1));
		}

		mock::start_era(1);

		// locked at era 1 until 4
		assert_ok!(Staking::unbond(Origin::signed(10), 1));
		// can't do more.
		assert_noop!(Staking::unbond(Origin::signed(10), 1), Error::<Test>::NoMoreChunks);

		mock::start_era(3);

		assert_noop!(Staking::unbond(Origin::signed(10), 1), Error::<Test>::NoMoreChunks);
		// free up.
		assert_ok!(Staking::withdraw_unbonded(Origin::signed(10)));

		// Can add again.
		assert_ok!(Staking::unbond(Origin::signed(10), 1));
		assert_eq!(Staking::ledger(&10).unwrap().unlocking.len(), 2);
	})
}

#[test]
fn rebond_works() {
	// * Should test
	// * Given an account being bonded [and chosen as a validator](not mandatory)
	// * it can unbond a portion of its funds from the stash account.
	// * it can re-bond a portion of the funds scheduled to unlock.
	ExtBuilder::default()
		.nominate(false)
		.build()
		.execute_with(|| {
			// Set payee to controller. avoids confusion
			assert_ok!(Staking::set_payee(
				Origin::signed(10),
				RewardDestination::Controller
			));

			// Give account 11 some large free balance greater than total
			let _ = Balances::make_free_balance_be(&11, 1000000);

			// confirm that 10 is a normal validator and gets paid at the end of the era.
			mock::start_era(1);

			// Initial state of 10
			assert_eq!(
				Staking::ledger(&10),
				Some(StakingLedger {
					stash: 11,
					total: 1000,
					active: 1000,
					unlocking: vec![],
					claimed_rewards: vec![],
				})
			);

			mock::start_era(2);
			assert_eq!(Staking::active_era().unwrap().index, 2);

			// Try to rebond some funds. We get an error since no fund is unbonded.
			assert_noop!(
				Staking::rebond(Origin::signed(10), 500),
				Error::<Test>::NoUnlockChunk,
			);

			// Unbond almost all of the funds in stash.
			Staking::unbond(Origin::signed(10), 900).unwrap();
			assert_eq!(
				Staking::ledger(&10),
				Some(StakingLedger {
					stash: 11,
					total: 1000,
					active: 100,
					unlocking: vec![UnlockChunk {
						value: 900,
						era: 2 + 3,
					}],
					claimed_rewards: vec![],
				})
			);

			// Re-bond all the funds unbonded.
			Staking::rebond(Origin::signed(10), 900).unwrap();
			assert_eq!(
				Staking::ledger(&10),
				Some(StakingLedger {
					stash: 11,
					total: 1000,
					active: 1000,
					unlocking: vec![],
					claimed_rewards: vec![],
				})
			);

			// Unbond almost all of the funds in stash.
			Staking::unbond(Origin::signed(10), 900).unwrap();
			assert_eq!(
				Staking::ledger(&10),
				Some(StakingLedger {
					stash: 11,
					total: 1000,
					active: 100,
					unlocking: vec![UnlockChunk { value: 900, era: 5 }],
					claimed_rewards: vec![],
				})
			);

			// Re-bond part of the funds unbonded.
			Staking::rebond(Origin::signed(10), 500).unwrap();
			assert_eq!(
				Staking::ledger(&10),
				Some(StakingLedger {
					stash: 11,
					total: 1000,
					active: 600,
					unlocking: vec![UnlockChunk { value: 400, era: 5 }],
					claimed_rewards: vec![],
				})
			);

			// Re-bond the remainder of the funds unbonded.
			Staking::rebond(Origin::signed(10), 500).unwrap();
			assert_eq!(
				Staking::ledger(&10),
				Some(StakingLedger {
					stash: 11,
					total: 1000,
					active: 1000,
					unlocking: vec![],
					claimed_rewards: vec![],
				})
			);

			// Unbond parts of the funds in stash.
			Staking::unbond(Origin::signed(10), 300).unwrap();
			Staking::unbond(Origin::signed(10), 300).unwrap();
			Staking::unbond(Origin::signed(10), 300).unwrap();
			assert_eq!(
				Staking::ledger(&10),
				Some(StakingLedger {
					stash: 11,
					total: 1000,
					active: 100,
					unlocking: vec![
						UnlockChunk { value: 300, era: 5 },
						UnlockChunk { value: 300, era: 5 },
						UnlockChunk { value: 300, era: 5 },
					],
					claimed_rewards: vec![],
				})
			);

			// Re-bond part of the funds unbonded.
			Staking::rebond(Origin::signed(10), 500).unwrap();
			assert_eq!(
				Staking::ledger(&10),
				Some(StakingLedger {
					stash: 11,
					total: 1000,
					active: 600,
					unlocking: vec![
						UnlockChunk { value: 300, era: 5 },
						UnlockChunk { value: 100, era: 5 },
					],
					claimed_rewards: vec![],
				})
			);
		})
}

#[test]
fn rebond_is_fifo() {
	// Rebond should proceed by reversing the most recent bond operations.
	ExtBuilder::default()
		.nominate(false)
		.build()
		.execute_with(|| {
			// Set payee to controller. avoids confusion
			assert_ok!(Staking::set_payee(
				Origin::signed(10),
				RewardDestination::Controller
			));

			// Give account 11 some large free balance greater than total
			let _ = Balances::make_free_balance_be(&11, 1000000);

			// confirm that 10 is a normal validator and gets paid at the end of the era.
			mock::start_era(1);

			// Initial state of 10
			assert_eq!(
				Staking::ledger(&10),
				Some(StakingLedger {
					stash: 11,
					total: 1000,
					active: 1000,
					unlocking: vec![],
					claimed_rewards: vec![],
				})
			);

			mock::start_era(2);

			// Unbond some of the funds in stash.
			Staking::unbond(Origin::signed(10), 400).unwrap();
			assert_eq!(
				Staking::ledger(&10),
				Some(StakingLedger {
					stash: 11,
					total: 1000,
					active: 600,
					unlocking: vec![
						UnlockChunk { value: 400, era: 2 + 3 },
					],
					claimed_rewards: vec![],
				})
			);

			mock::start_era(3);

			// Unbond more of the funds in stash.
			Staking::unbond(Origin::signed(10), 300).unwrap();
			assert_eq!(
				Staking::ledger(&10),
				Some(StakingLedger {
					stash: 11,
					total: 1000,
					active: 300,
					unlocking: vec![
						UnlockChunk { value: 400, era: 2 + 3 },
						UnlockChunk { value: 300, era: 3 + 3 },
					],
					claimed_rewards: vec![],
				})
			);

			mock::start_era(4);

			// Unbond yet more of the funds in stash.
			Staking::unbond(Origin::signed(10), 200).unwrap();
			assert_eq!(
				Staking::ledger(&10),
				Some(StakingLedger {
					stash: 11,
					total: 1000,
					active: 100,
					unlocking: vec![
						UnlockChunk { value: 400, era: 2 + 3 },
						UnlockChunk { value: 300, era: 3 + 3 },
						UnlockChunk { value: 200, era: 4 + 3 },
					],
					claimed_rewards: vec![],
				})
			);

			// Re-bond half of the unbonding funds.
			Staking::rebond(Origin::signed(10), 400).unwrap();
			assert_eq!(
				Staking::ledger(&10),
				Some(StakingLedger {
					stash: 11,
					total: 1000,
					active: 500,
					unlocking: vec![
						UnlockChunk { value: 400, era: 2 + 3 },
						UnlockChunk { value: 100, era: 3 + 3 },
					],
					claimed_rewards: vec![],
				})
			);
		})
}

#[test]
fn reward_to_stake_works() {
	ExtBuilder::default().nominate(false).fair(false).build_and_execute(|| {
		// Confirm validator count is 2
		assert_eq!(Staking::validator_count(), 2);
		// Confirm account 10 and 20 are validators
		assert!(<Validators<Test>>::contains_key(&11) && <Validators<Test>>::contains_key(&21));

		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 11).total, 1000);
		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 21).total, 2000);

		// Give the man some money.
		let _ = Balances::make_free_balance_be(&10, 1000);
		let _ = Balances::make_free_balance_be(&20, 1000);

		// Bypass logic and change current exposure
		ErasStakers::<Test>::insert(0, 21, Exposure { total: 69, own: 69, others: vec![] });

		// Now lets lower account 20 stake
		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 21).total, 69);
		<Ledger<Test>>::insert(&20, StakingLedger { stash: 21, total: 69, active: 69, unlocking: vec![], claimed_rewards: vec![] });

		// Compute total payout now for whole duration as other parameter won't change
		let total_payout_0 = current_total_payout_for_duration(3000);
		assert!(total_payout_0 > 100); // Test is meaningful if reward something
		<Module<Test>>::reward_by_ids(vec![(11, 1)]);
		<Module<Test>>::reward_by_ids(vec![(21, 1)]);

		// New era --> rewards are paid --> stakes are changed
		mock::start_era(1);
		mock::make_all_reward_payment(0);

		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 11).total, 1000);
		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 21).total, 69);

		let _11_balance = Balances::free_balance(&11);
		assert_eq!(_11_balance, 1000 + total_payout_0 / 2);

		// Trigger another new era as the info are frozen before the era start.
		mock::start_era(2);

		// -- new infos
		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 11).total, 1000 + total_payout_0 / 2);
		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 21).total, 69 + total_payout_0 / 2);
	});
}

#[test]
fn on_free_balance_zero_stash_removes_validator() {
	// Tests that validator storage items are cleaned up when stash is empty
	// Tests that storage items are untouched when controller is empty
	ExtBuilder::default().existential_deposit(10).build_and_execute(|| {
		// Check the balance of the validator account
		assert_eq!(Balances::free_balance(10), 256);
		// Check the balance of the stash account
		assert_eq!(Balances::free_balance(11), 256000);
		// Check these two accounts are bonded
		assert_eq!(Staking::bonded(&11), Some(10));

		// Set some storage items which we expect to be cleaned up
		// Set payee information
		assert_ok!(Staking::set_payee(Origin::signed(10), RewardDestination::Stash));

		// Check storage items that should be cleaned up
		assert!(<Ledger<Test>>::contains_key(&10));
		assert!(<Bonded<Test>>::contains_key(&11));
		assert!(<Validators<Test>>::contains_key(&11));
		assert!(<Payee<Test>>::contains_key(&11));

		// Reduce free_balance of controller to 0
		let _ = Balances::slash(&10, Balance::max_value());

		// Check the balance of the stash account has not been touched
		assert_eq!(Balances::free_balance(11), 256000);
		// Check these two accounts are still bonded
		assert_eq!(Staking::bonded(&11), Some(10));

		// Check storage items have not changed
		assert!(<Ledger<Test>>::contains_key(&10));
		assert!(<Bonded<Test>>::contains_key(&11));
		assert!(<Validators<Test>>::contains_key(&11));
		assert!(<Payee<Test>>::contains_key(&11));

		// Reduce free_balance of stash to 0
		let _ = Balances::slash(&11, Balance::max_value());
		// Check total balance of stash
		assert_eq!(Balances::total_balance(&11), 0);

		// Reap the stash
		assert_ok!(Staking::reap_stash(Origin::NONE, 11));

		// Check storage items do not exist
		assert!(!<Ledger<Test>>::contains_key(&10));
		assert!(!<Bonded<Test>>::contains_key(&11));
		assert!(!<Validators<Test>>::contains_key(&11));
		assert!(!<Nominators<Test>>::contains_key(&11));
		assert!(!<Payee<Test>>::contains_key(&11));
	});
}

#[test]
fn on_free_balance_zero_stash_removes_nominator() {
	// Tests that nominator storage items are cleaned up when stash is empty
	// Tests that storage items are untouched when controller is empty
	ExtBuilder::default().existential_deposit(10).build_and_execute(|| {
		// Make 10 a nominator
		assert_ok!(Staking::nominate(Origin::signed(10), vec![20]));
		// Check that account 10 is a nominator
		assert!(<Nominators<Test>>::contains_key(11));
		// Check the balance of the nominator account
		assert_eq!(Balances::free_balance(10), 256);
		// Check the balance of the stash account
		assert_eq!(Balances::free_balance(11), 256000);

		// Set payee information
		assert_ok!(Staking::set_payee(Origin::signed(10), RewardDestination::Stash));

		// Check storage items that should be cleaned up
		assert!(<Ledger<Test>>::contains_key(&10));
		assert!(<Bonded<Test>>::contains_key(&11));
		assert!(<Nominators<Test>>::contains_key(&11));
		assert!(<Payee<Test>>::contains_key(&11));

		// Reduce free_balance of controller to 0
		let _ = Balances::slash(&10, Balance::max_value());
		// Check total balance of account 10
		assert_eq!(Balances::total_balance(&10), 0);

		// Check the balance of the stash account has not been touched
		assert_eq!(Balances::free_balance(11), 256000);
		// Check these two accounts are still bonded
		assert_eq!(Staking::bonded(&11), Some(10));

		// Check storage items have not changed
		assert!(<Ledger<Test>>::contains_key(&10));
		assert!(<Bonded<Test>>::contains_key(&11));
		assert!(<Nominators<Test>>::contains_key(&11));
		assert!(<Payee<Test>>::contains_key(&11));

		// Reduce free_balance of stash to 0
		let _ = Balances::slash(&11, Balance::max_value());
		// Check total balance of stash
		assert_eq!(Balances::total_balance(&11), 0);

		// Reap the stash
		assert_ok!(Staking::reap_stash(Origin::NONE, 11));

		// Check storage items do not exist
		assert!(!<Ledger<Test>>::contains_key(&10));
		assert!(!<Bonded<Test>>::contains_key(&11));
		assert!(!<Validators<Test>>::contains_key(&11));
		assert!(!<Nominators<Test>>::contains_key(&11));
		assert!(!<Payee<Test>>::contains_key(&11));
	});
}


#[test]
fn switching_roles() {
	// Test that it should be possible to switch between roles (nominator, validator, idle) with minimal overhead.
	ExtBuilder::default().nominate(false).build_and_execute(|| {
		// Reset reward destination
		for i in &[10, 20] { assert_ok!(Staking::set_payee(Origin::signed(*i), RewardDestination::Controller)); }

		assert_eq_uvec!(validator_controllers(), vec![20, 10]);

		// put some money in account that we'll use.
		for i in 1..7 { let _ = Balances::deposit_creating(&i, 5000); }

		// add 2 nominators
		assert_ok!(Staking::bond(Origin::signed(1), 2, 2000, RewardDestination::Controller));
		assert_ok!(Staking::nominate(Origin::signed(2), vec![11, 5]));

		assert_ok!(Staking::bond(Origin::signed(3), 4, 500, RewardDestination::Controller));
		assert_ok!(Staking::nominate(Origin::signed(4), vec![21, 1]));

		// add a new validator candidate
		assert_ok!(Staking::bond(Origin::signed(5), 6, 1000, RewardDestination::Controller));
		assert_ok!(Staking::validate(Origin::signed(6), ValidatorPrefs::default()));

		mock::start_era(1);

		// with current nominators 10 and 5 have the most stake
		assert_eq_uvec!(validator_controllers(), vec![6, 10]);

		// 2 decides to be a validator. Consequences:
		assert_ok!(Staking::validate(Origin::signed(2), ValidatorPrefs::default()));
		// new stakes:
		// 10: 1000 self vote
		// 20: 1000 self vote + 250 vote
		// 6 : 1000 self vote
		// 2 : 2000 self vote + 250 vote.
		// Winners: 20 and 2

		mock::start_era(2);

		assert_eq_uvec!(validator_controllers(), vec![2, 20]);
	});
}

#[test]
fn wrong_vote_is_null() {
	ExtBuilder::default().nominate(false).validator_pool(true).build_and_execute(|| {
		assert_eq_uvec!(validator_controllers(), vec![40, 30]);

		// put some money in account that we'll use.
		for i in 1..3 { let _ = Balances::deposit_creating(&i, 5000); }

		// add 1 nominators
		assert_ok!(Staking::bond(Origin::signed(1), 2, 2000, RewardDestination::default()));
		assert_ok!(Staking::nominate(Origin::signed(2), vec![
			11, 21, 			// good votes
			1, 2, 15, 1000, 25  // crap votes. No effect.
		]));

		// new block
		mock::start_era(1);

		assert_eq_uvec!(validator_controllers(), vec![20, 10]);
	});
}

#[test]
fn bond_with_no_staked_value() {
	// Behavior when someone bonds with no staked value.
	// Particularly when she votes and the candidate is elected.
	ExtBuilder::default()
		.validator_count(3)
		.existential_deposit(5)
		.nominate(false)
		.minimum_validator_count(1)
		.build()
		.execute_with(|| {
			// Can't bond with 1
			assert_noop!(
				Staking::bond(Origin::signed(1), 2, 1, RewardDestination::Controller),
				Error::<Test>::InsufficientValue,
			);
			// bonded with absolute minimum value possible.
			assert_ok!(Staking::bond(Origin::signed(1), 2, 5, RewardDestination::Controller));
			assert_eq!(Balances::locks(&1)[0].amount, 5);

			// unbonding even 1 will cause all to be unbonded.
			assert_ok!(Staking::unbond(Origin::signed(2), 1));
			assert_eq!(
				Staking::ledger(2),
				Some(StakingLedger {
					stash: 1,
					active: 0,
					total: 5,
					unlocking: vec![UnlockChunk {value: 5, era: 3}],
					claimed_rewards: vec![],
				})
			);

			mock::start_era(1);
			mock::start_era(2);

			// not yet removed.
			assert_ok!(Staking::withdraw_unbonded(Origin::signed(2)));
			assert!(Staking::ledger(2).is_some());
			assert_eq!(Balances::locks(&1)[0].amount, 5);

			mock::start_era(3);

			// poof. Account 1 is removed from the staking system.
			assert_ok!(Staking::withdraw_unbonded(Origin::signed(2)));
			assert!(Staking::ledger(2).is_none());
			assert_eq!(Balances::locks(&1).len(), 0);
		});
}

#[test]
fn bond_with_little_staked_value_bounded() {
	// Behavior when someone bonds with little staked value.
	// Particularly when she votes and the candidate is elected.
	ExtBuilder::default()
		.validator_count(3)
		.nominate(false)
		.minimum_validator_count(1)
		.build()
		.execute_with(|| {
			// setup
			assert_ok!(Staking::chill(Origin::signed(30)));
			assert_ok!(Staking::set_payee(Origin::signed(10), RewardDestination::Controller));
			let init_balance_2 = Balances::free_balance(&2);
			let init_balance_10 = Balances::free_balance(&10);

			// Stingy validator.
			assert_ok!(Staking::bond(Origin::signed(1), 2, 1, RewardDestination::Controller));
			assert_ok!(Staking::validate(Origin::signed(2), ValidatorPrefs::default()));

			// reward era 0
			let total_payout_0 = current_total_payout_for_duration(3000);
			assert!(total_payout_0 > 100); // Test is meaningful if reward something
			reward_all_elected();
			mock::start_era(1);
			mock::make_all_reward_payment(0);

			// 2 is elected.
			assert_eq_uvec!(validator_controllers(), vec![20, 10, 2]);
			// And has minimal stake
			assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 2).total, 0);

			// Old ones are rewarded.
			assert_eq!(Balances::free_balance(10), init_balance_10 + total_payout_0 / 3);
			// no rewards paid to 2. This was initial election.
			assert_eq!(Balances::free_balance(2), init_balance_2);

			// reward era 1
			let total_payout_1 = current_total_payout_for_duration(3000);
			assert!(total_payout_1 > 100); // Test is meaningful if reward something
			reward_all_elected();
			mock::start_era(2);
			mock::make_all_reward_payment(1);

			assert_eq_uvec!(validator_controllers(), vec![20, 10, 2]);
			assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 2).total, 0);

			assert_eq!(Balances::free_balance(2), init_balance_2 + total_payout_1 / 3);
			assert_eq!(
				Balances::free_balance(&10),
				init_balance_10 + total_payout_0 / 3 + total_payout_1 / 3,
			);
		});
}

#[test]
fn new_era_elects_correct_number_of_validators() {
	ExtBuilder::default()
		.nominate(true)
		.validator_pool(true)
		.fair(true)
		.validator_count(1)
		.build()
		.execute_with(|| {
			assert_eq!(Staking::validator_count(), 1);
			assert_eq!(validator_controllers().len(), 1);

			Session::on_initialize(System::block_number());

			assert_eq!(validator_controllers().len(), 1);
		})
}

#[test]
fn phragmen_should_not_overflow() {
	ExtBuilder::default().nominate(false).build_and_execute(|| {
		// This is the maximum value that we can have as the outcome of CurrencyToVote.
		type Votes = u64;

		let _ = Staking::chill(Origin::signed(10));
		let _ = Staking::chill(Origin::signed(20));

		bond_validator(3, 2, Votes::max_value() as Balance);
		bond_validator(5, 4, Votes::max_value() as Balance);

		bond_nominator(7, 6, Votes::max_value() as Balance, vec![3, 5]);
		bond_nominator(9, 8, Votes::max_value() as Balance, vec![3, 5]);

		mock::start_era(1);

		assert_eq_uvec!(validator_controllers(), vec![4, 2]);

		// We can safely convert back to values within [u64, u128].
		assert!(Staking::eras_stakers(active_era(), 3).total > Votes::max_value() as Balance);
		assert!(Staking::eras_stakers(active_era(), 5).total > Votes::max_value() as Balance);
	})
}

#[test]
fn reward_validator_slashing_validator_does_not_overflow() {
	ExtBuilder::default().build_and_execute(|| {
		let stake = u64::max_value() as Balance * 2;
		let reward_slash = u64::max_value() as Balance * 2;

		// Assert multiplication overflows in balance arithmetic.
		assert!(stake.checked_mul(reward_slash).is_none());

		// Set staker
		let _ = Balances::make_free_balance_be(&11, stake);

		let exposure = Exposure::<AccountId, Balance> { total: stake, own: stake, others: vec![] };
		let reward = EraRewardPoints::<AccountId> {
			total: 1,
			individual: vec![(11, 1)].into_iter().collect(),
		};

		// Check reward
		ErasRewardPoints::<Test>::insert(0, reward);
		ErasStakers::<Test>::insert(0, 11, &exposure);
		ErasStakersClipped::<Test>::insert(0, 11, exposure);
		ErasValidatorReward::<Test>::insert(0, stake);
		assert_ok!(Staking::payout_stakers(Origin::signed(1337), 11, 0));
		assert_eq!(Balances::total_balance(&11), stake * 2);

		// Set staker
		let _ = Balances::make_free_balance_be(&11, stake);
		let _ = Balances::make_free_balance_be(&2, stake);

		// only slashes out of bonded stake are applied. without this line,
		// it is 0.
		Staking::bond(Origin::signed(2), 20000, stake - 1, RewardDestination::default()).unwrap();
		// Override exposure of 11
		ErasStakers::<Test>::insert(0, 11, Exposure {
			total: stake,
			own: 1,
			others: vec![ IndividualExposure { who: 2, value: stake - 1 }]
		});

		// Check slashing
		on_offence_now(
			&[
				OffenceDetails {
					offender: (11, Staking::eras_stakers(Staking::active_era().unwrap().index, 11)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(100)],
		);

		assert_eq!(Balances::total_balance(&11), stake - 1);
		assert_eq!(Balances::total_balance(&2), 1);
	})
}

#[test]
fn reward_from_authorship_event_handler_works() {
	ExtBuilder::default().build_and_execute(|| {
		use pallet_authorship::EventHandler;

		assert_eq!(<pallet_authorship::Module<Test>>::author(), 11);

		<Module<Test>>::note_author(11);
		<Module<Test>>::note_uncle(21, 1);
		// Rewarding the same two times works.
		<Module<Test>>::note_uncle(11, 1);

		// Not mandatory but must be coherent with rewards
		assert_eq_uvec!(Session::validators(), vec![11, 21]);

		// 21 is rewarded as an uncle producer
		// 11 is rewarded as a block producer and uncle referencer and uncle producer
		assert_eq!(
			ErasRewardPoints::<Test>::get(Staking::active_era().unwrap().index),
			EraRewardPoints {
				individual: vec![(11, 20 + 2 * 2 + 1), (21, 1)].into_iter().collect(),
				total: 26,
			},
		);
	})
}

#[test]
fn add_reward_points_fns_works() {
	ExtBuilder::default().build_and_execute(|| {
		// Not mandatory but must be coherent with rewards
		assert_eq!(Session::validators(), vec![21, 11]);

		<Module<Test>>::reward_by_ids(vec![
			(21, 1),
			(11, 1),
			(11, 1),
		]);

		<Module<Test>>::reward_by_ids(vec![
			(21, 1),
			(11, 1),
			(11, 1),
		]);

		assert_eq!(
			ErasRewardPoints::<Test>::get(Staking::active_era().unwrap().index),
			EraRewardPoints {
				individual: vec![(11, 4), (21, 2)].into_iter().collect(),
				total: 6,
			},
		);
	})
}

#[test]
fn unbonded_balance_is_not_slashable() {
	ExtBuilder::default().build_and_execute(|| {
		// total amount staked is slashable.
		assert_eq!(Staking::slashable_balance_of(&11), 1000);

		assert_ok!(Staking::unbond(Origin::signed(10),  800));

		// only the active portion.
		assert_eq!(Staking::slashable_balance_of(&11), 200);
	})
}

#[test]
fn era_is_always_same_length() {
	// This ensures that the sessions is always of the same length if there is no forcing no
	// session changes.
	ExtBuilder::default().build_and_execute(|| {
		let session_per_era = <SessionsPerEra as Get<SessionIndex>>::get();

		mock::start_era(1);
		assert_eq!(Staking::eras_start_session_index(current_era()).unwrap(), session_per_era);

		mock::start_era(2);
		assert_eq!(Staking::eras_start_session_index(current_era()).unwrap(), session_per_era * 2u32);

		let session = Session::current_index();
		ForceEra::put(Forcing::ForceNew);
		advance_session();
		advance_session();
		assert_eq!(current_era(), 3);
		assert_eq!(Staking::eras_start_session_index(current_era()).unwrap(), session + 2);

		mock::start_era(4);
		assert_eq!(Staking::eras_start_session_index(current_era()).unwrap(), session + 2u32 + session_per_era);
	});
}

#[test]
fn offence_forces_new_era() {
	ExtBuilder::default().build_and_execute(|| {
		on_offence_now(
			&[OffenceDetails {
				offender: (
					11,
					Staking::eras_stakers(Staking::active_era().unwrap().index, 11),
				),
				reporters: vec![],
			}],
			&[Perbill::from_percent(5)],
		);

		assert_eq!(Staking::force_era(), Forcing::ForceNew);
	});
}

#[test]
fn offence_ensures_new_era_without_clobbering() {
	ExtBuilder::default().build_and_execute(|| {
		assert_ok!(Staking::force_new_era_always(Origin::ROOT));
		assert_eq!(Staking::force_era(), Forcing::ForceAlways);

		on_offence_now(
			&[OffenceDetails {
				offender: (
					11,
					Staking::eras_stakers(Staking::active_era().unwrap().index, 11),
				),
				reporters: vec![],
			}],
			&[Perbill::from_percent(5)],
		);

		assert_eq!(Staking::force_era(), Forcing::ForceAlways);
	});
}

#[test]
fn offence_deselects_validator_even_when_slash_is_zero() {
	ExtBuilder::default().build_and_execute(|| {
		assert!(Session::validators().contains(&11));
		assert!(<Validators<Test>>::contains_key(11));

		on_offence_now(
			&[OffenceDetails {
				offender: (
					11,
					Staking::eras_stakers(Staking::active_era().unwrap().index, 11),
				),
				reporters: vec![],
			}],
			&[Perbill::from_percent(0)],
		);

		assert_eq!(Staking::force_era(), Forcing::ForceNew);
		assert!(!<Validators<Test>>::contains_key(11));

		mock::start_era(1);

		assert!(!Session::validators().contains(&11));
		assert!(!<Validators<Test>>::contains_key(11));
	});
}

#[test]
fn slashing_performed_according_exposure() {
	// This test checks that slashing is performed according the exposure (or more precisely,
	// historical exposure), not the current balance.
	ExtBuilder::default().build_and_execute(|| {
		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 11).own, 1000);

		// Handle an offence with a historical exposure.
		on_offence_now(
			&[OffenceDetails {
				offender: (
					11,
					Exposure {
						total: 500,
						own: 500,
						others: vec![],
					},
				),
				reporters: vec![],
			}],
			&[Perbill::from_percent(50)],
		);

		// The stash account should be slashed for 250 (50% of 500).
		assert_eq!(Balances::free_balance(11), 1000 - 250);
	});
}

#[test]
fn slash_in_old_span_does_not_deselect() {
	ExtBuilder::default().build_and_execute(|| {
		mock::start_era(1);

		assert!(<Validators<Test>>::contains_key(11));
		assert!(Session::validators().contains(&11));

		on_offence_now(
			&[OffenceDetails {
				offender: (
					11,
					Staking::eras_stakers(Staking::active_era().unwrap().index, 11),
				),
				reporters: vec![],
			}],
			&[Perbill::from_percent(0)],
		);

		assert_eq!(Staking::force_era(), Forcing::ForceNew);
		assert!(!<Validators<Test>>::contains_key(11));

		mock::start_era(2);

		Staking::validate(Origin::signed(10), Default::default()).unwrap();
		assert_eq!(Staking::force_era(), Forcing::NotForcing);
		assert!(<Validators<Test>>::contains_key(11));
		assert!(!Session::validators().contains(&11));

		mock::start_era(3);

		// this staker is in a new slashing span now, having re-registered after
		// their prior slash.

		on_offence_in_era(
			&[OffenceDetails {
				offender: (
					11,
					Staking::eras_stakers(Staking::active_era().unwrap().index, 11),
				),
				reporters: vec![],
			}],
			&[Perbill::from_percent(0)],
			1,
		);

		// not forcing for zero-slash and previous span.
		assert_eq!(Staking::force_era(), Forcing::NotForcing);
		assert!(<Validators<Test>>::contains_key(11));
		assert!(Session::validators().contains(&11));

		on_offence_in_era(
			&[OffenceDetails {
				offender: (
					11,
					Staking::eras_stakers(Staking::active_era().unwrap().index, 11),
				),
				reporters: vec![],
			}],
			// NOTE: A 100% slash here would clean up the account, causing de-registration.
			&[Perbill::from_percent(95)],
			1,
		);

		// or non-zero.
		assert_eq!(Staking::force_era(), Forcing::NotForcing);
		assert!(<Validators<Test>>::contains_key(11));
		assert!(Session::validators().contains(&11));
	});
}

#[test]
fn reporters_receive_their_slice() {
	// This test verifies that the reporters of the offence receive their slice from the slashed
	// amount.
	ExtBuilder::default().build_and_execute(|| {
		// The reporters' reward is calculated from the total exposure.
		let initial_balance = 1125;

		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 11).total, initial_balance);

		on_offence_now(
			&[OffenceDetails {
				offender: (
					11,
					Staking::eras_stakers(Staking::active_era().unwrap().index, 11),
				),
				reporters: vec![1, 2],
			}],
			&[Perbill::from_percent(50)],
		);

		// F1 * (reward_proportion * slash - 0)
		// 50% * (10% * initial_balance / 2)
		let reward = (initial_balance / 20) / 2;
		let reward_each = reward / 2; // split into two pieces.
		assert_eq!(Balances::free_balance(1), 10 + reward_each);
		assert_eq!(Balances::free_balance(2), 20 + reward_each);
	});
}

#[test]
fn subsequent_reports_in_same_span_pay_out_less() {
	// This test verifies that the reporters of the offence receive their slice from the slashed
	// amount, but less and less if they submit multiple reports in one span.
	ExtBuilder::default().build_and_execute(|| {
		// The reporters' reward is calculated from the total exposure.
		let initial_balance = 1125;

		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 11).total, initial_balance);

		on_offence_now(
			&[OffenceDetails {
				offender: (
					11,
					Staking::eras_stakers(Staking::active_era().unwrap().index, 11),
				),
				reporters: vec![1],
			}],
			&[Perbill::from_percent(20)],
		);

		// F1 * (reward_proportion * slash - 0)
		// 50% * (10% * initial_balance * 20%)
		let reward = (initial_balance / 5) / 20;
		assert_eq!(Balances::free_balance(1), 10 + reward);

		on_offence_now(
			&[OffenceDetails {
				offender: (
					11,
					Staking::eras_stakers(Staking::active_era().unwrap().index, 11),
				),
				reporters: vec![1],
			}],
			&[Perbill::from_percent(50)],
		);

		let prior_payout = reward;

		// F1 * (reward_proportion * slash - prior_payout)
		// 50% * (10% * (initial_balance / 2) - prior_payout)
		let reward = ((initial_balance / 20) - prior_payout) / 2;
		assert_eq!(Balances::free_balance(1), 10 + prior_payout + reward);
	});
}

#[test]
fn invulnerables_are_not_slashed() {
	// For invulnerable validators no slashing is performed.
	ExtBuilder::default().invulnerables(vec![11]).build_and_execute(|| {
		assert_eq!(Balances::free_balance(11), 1000);
		assert_eq!(Balances::free_balance(21), 2000);

		let exposure = Staking::eras_stakers(Staking::active_era().unwrap().index, 21);
		let initial_balance = Staking::slashable_balance_of(&21);

		let nominator_balances: Vec<_> = exposure.others
			.iter().map(|o| Balances::free_balance(&o.who)).collect();

		on_offence_now(
			&[
				OffenceDetails {
					offender: (11, Staking::eras_stakers(Staking::active_era().unwrap().index, 11)),
					reporters: vec![],
				},
				OffenceDetails {
					offender: (21, Staking::eras_stakers(Staking::active_era().unwrap().index, 21)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(50), Perbill::from_percent(20)],
		);

		// The validator 11 hasn't been slashed, but 21 has been.
		assert_eq!(Balances::free_balance(11), 1000);
		// 2000 - (0.2 * initial_balance)
		assert_eq!(Balances::free_balance(21), 2000 - (2 * initial_balance / 10));

		// ensure that nominators were slashed as well.
		for (initial_balance, other) in nominator_balances.into_iter().zip(exposure.others) {
			assert_eq!(
				Balances::free_balance(&other.who),
				initial_balance - (2 * other.value / 10),
			);
		}
	});
}

#[test]
fn dont_slash_if_fraction_is_zero() {
	// Don't slash if the fraction is zero.
	ExtBuilder::default().build_and_execute(|| {
		assert_eq!(Balances::free_balance(11), 1000);

		on_offence_now(
			&[OffenceDetails {
				offender: (
					11,
					Staking::eras_stakers(Staking::active_era().unwrap().index, 11),
				),
				reporters: vec![],
			}],
			&[Perbill::from_percent(0)],
		);

		// The validator hasn't been slashed. The new era is not forced.
		assert_eq!(Balances::free_balance(11), 1000);
		assert_eq!(Staking::force_era(), Forcing::ForceNew);
	});
}

#[test]
fn only_slash_for_max_in_era() {
	// multiple slashes within one era are only applied if it is more than any previous slash in the
	// same era.
	ExtBuilder::default().build_and_execute(|| {
		assert_eq!(Balances::free_balance(11), 1000);

		on_offence_now(
			&[
				OffenceDetails {
					offender: (11, Staking::eras_stakers(Staking::active_era().unwrap().index, 11)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(50)],
		);

		// The validator has been slashed and has been force-chilled.
		assert_eq!(Balances::free_balance(11), 500);
		assert_eq!(Staking::force_era(), Forcing::ForceNew);

		on_offence_now(
			&[
				OffenceDetails {
					offender: (11, Staking::eras_stakers(Staking::active_era().unwrap().index, 11)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(25)],
		);

		// The validator has not been slashed additionally.
		assert_eq!(Balances::free_balance(11), 500);

		on_offence_now(
			&[
				OffenceDetails {
					offender: (11, Staking::eras_stakers(Staking::active_era().unwrap().index, 11)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(60)],
		);

		// The validator got slashed 10% more.
		assert_eq!(Balances::free_balance(11), 400);
	})
}

#[test]
fn garbage_collection_after_slashing() {
	// ensures that `SlashingSpans` and `SpanSlash` of an account is removed after reaping.
	ExtBuilder::default().existential_deposit(2).build_and_execute(|| {
		assert_eq!(Balances::free_balance(11), 256_000);

		on_offence_now(
			&[
				OffenceDetails {
					offender: (11, Staking::eras_stakers(Staking::active_era().unwrap().index, 11)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(10)],
		);

		assert_eq!(Balances::free_balance(11), 256_000 - 25_600);
		assert!(<Staking as crate::Store>::SlashingSpans::get(&11).is_some());
		assert_eq!(<Staking as crate::Store>::SpanSlash::get(&(11, 0)).amount_slashed(), &25_600);

		on_offence_now(
			&[
				OffenceDetails {
					offender: (11, Staking::eras_stakers(Staking::active_era().unwrap().index, 11)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(100)],
		);

		// validator and nominator slash in era are garbage-collected by era change,
		// so we don't test those here.

		assert_eq!(Balances::free_balance(11), 0);
		assert_eq!(Balances::total_balance(&11), 0);

		assert_ok!(Staking::reap_stash(Origin::NONE, 11));

		assert!(<Staking as crate::Store>::SlashingSpans::get(&11).is_none());
		assert_eq!(<Staking as crate::Store>::SpanSlash::get(&(11, 0)).amount_slashed(), &0);
	})
}

#[test]
fn garbage_collection_on_window_pruning() {
	// ensures that `ValidatorSlashInEra` and `NominatorSlashInEra` are cleared after
	// `BondingDuration`.
	ExtBuilder::default().build_and_execute(|| {
		mock::start_era(1);

		assert_eq!(Balances::free_balance(11), 1000);
		let now = Staking::active_era().unwrap().index;

		let exposure = Staking::eras_stakers(now, 11);
		assert_eq!(Balances::free_balance(101), 2000);
		let nominated_value = exposure.others.iter().find(|o| o.who == 101).unwrap().value;

		on_offence_now(
			&[
				OffenceDetails {
					offender: (11, Staking::eras_stakers(now, 11)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(10)],
		);

		assert_eq!(Balances::free_balance(11), 900);
		assert_eq!(Balances::free_balance(101), 2000 - (nominated_value / 10));

		assert!(<Staking as crate::Store>::ValidatorSlashInEra::get(&now, &11).is_some());
		assert!(<Staking as crate::Store>::NominatorSlashInEra::get(&now, &101).is_some());

		// + 1 because we have to exit the bonding window.
		for era in (0..(BondingDuration::get() + 1)).map(|offset| offset + now + 1) {
			assert!(<Staking as crate::Store>::ValidatorSlashInEra::get(&now, &11).is_some());
			assert!(<Staking as crate::Store>::NominatorSlashInEra::get(&now, &101).is_some());

			mock::start_era(era);
		}

		assert!(<Staking as crate::Store>::ValidatorSlashInEra::get(&now, &11).is_none());
		assert!(<Staking as crate::Store>::NominatorSlashInEra::get(&now, &101).is_none());
	})
}

#[test]
fn slashing_nominators_by_span_max() {
	ExtBuilder::default().build_and_execute(|| {
		mock::start_era(1);
		mock::start_era(2);
		mock::start_era(3);

		assert_eq!(Balances::free_balance(11), 1000);
		assert_eq!(Balances::free_balance(21), 2000);
		assert_eq!(Balances::free_balance(101), 2000);
		assert_eq!(Staking::slashable_balance_of(&21), 1000);

		let exposure_11 = Staking::eras_stakers(Staking::active_era().unwrap().index, 11);
		let exposure_21 = Staking::eras_stakers(Staking::active_era().unwrap().index, 21);
		let nominated_value_11 = exposure_11.others.iter().find(|o| o.who == 101).unwrap().value;
		let nominated_value_21 = exposure_21.others.iter().find(|o| o.who == 101).unwrap().value;

		on_offence_in_era(
			&[
				OffenceDetails {
					offender: (11, Staking::eras_stakers(Staking::active_era().unwrap().index, 11)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(10)],
			2,
		);

		assert_eq!(Balances::free_balance(11), 900);

		let slash_1_amount = Perbill::from_percent(10) * nominated_value_11;
		assert_eq!(Balances::free_balance(101), 2000 - slash_1_amount);

		let expected_spans = vec![
			slashing::SlashingSpan { index: 1, start: 4, length: None },
			slashing::SlashingSpan { index: 0, start: 0, length: Some(4) },
		];

		let get_span = |account| <Staking as crate::Store>::SlashingSpans::get(&account).unwrap();

		assert_eq!(
			get_span(11).iter().collect::<Vec<_>>(),
			expected_spans,
		);

		assert_eq!(
			get_span(101).iter().collect::<Vec<_>>(),
			expected_spans,
		);

		// second slash: higher era, higher value, same span.
		on_offence_in_era(
			&[
				OffenceDetails {
					offender: (21, Staking::eras_stakers(Staking::active_era().unwrap().index, 21)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(30)],
			3,
		);

		// 11 was not further slashed, but 21 and 101 were.
		assert_eq!(Balances::free_balance(11), 900);
		assert_eq!(Balances::free_balance(21), 1700);

		let slash_2_amount = Perbill::from_percent(30) * nominated_value_21;
		assert!(slash_2_amount > slash_1_amount);

		// only the maximum slash in a single span is taken.
		assert_eq!(Balances::free_balance(101), 2000 - slash_2_amount);

		// third slash: in same era and on same validator as first, higher
		// in-era value, but lower slash value than slash 2.
		on_offence_in_era(
			&[
				OffenceDetails {
					offender: (11, Staking::eras_stakers(Staking::active_era().unwrap().index, 11)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(20)],
			2,
		);

		// 11 was further slashed, but 21 and 101 were not.
		assert_eq!(Balances::free_balance(11), 800);
		assert_eq!(Balances::free_balance(21), 1700);

		let slash_3_amount = Perbill::from_percent(20) * nominated_value_21;
		assert!(slash_3_amount < slash_2_amount);
		assert!(slash_3_amount > slash_1_amount);

		// only the maximum slash in a single span is taken.
		assert_eq!(Balances::free_balance(101), 2000 - slash_2_amount);
	});
}

#[test]
fn slashes_are_summed_across_spans() {
	ExtBuilder::default().build_and_execute(|| {
		mock::start_era(1);
		mock::start_era(2);
		mock::start_era(3);

		assert_eq!(Balances::free_balance(21), 2000);
		assert_eq!(Staking::slashable_balance_of(&21), 1000);

		let get_span = |account| <Staking as crate::Store>::SlashingSpans::get(&account).unwrap();

		on_offence_now(
			&[
				OffenceDetails {
					offender: (21, Staking::eras_stakers(Staking::active_era().unwrap().index, 21)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(10)],
		);

		let expected_spans = vec![
			slashing::SlashingSpan { index: 1, start: 4, length: None },
			slashing::SlashingSpan { index: 0, start: 0, length: Some(4) },
		];

		assert_eq!(get_span(21).iter().collect::<Vec<_>>(), expected_spans);
		assert_eq!(Balances::free_balance(21), 1900);

		// 21 has been force-chilled. re-signal intent to validate.
		Staking::validate(Origin::signed(20), Default::default()).unwrap();

		mock::start_era(4);

		assert_eq!(Staking::slashable_balance_of(&21), 900);

		on_offence_now(
			&[
				OffenceDetails {
					offender: (21, Staking::eras_stakers(Staking::active_era().unwrap().index, 21)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(10)],
		);

		let expected_spans = vec![
			slashing::SlashingSpan { index: 2, start: 5, length: None },
			slashing::SlashingSpan { index: 1, start: 4, length: Some(1) },
			slashing::SlashingSpan { index: 0, start: 0, length: Some(4) },
		];

		assert_eq!(get_span(21).iter().collect::<Vec<_>>(), expected_spans);
		assert_eq!(Balances::free_balance(21), 1810);
	});
}

#[test]
fn deferred_slashes_are_deferred() {
	ExtBuilder::default().slash_defer_duration(2).build_and_execute(|| {
		mock::start_era(1);

		assert_eq!(Balances::free_balance(11), 1000);

		let exposure = Staking::eras_stakers(Staking::active_era().unwrap().index, 11);
		assert_eq!(Balances::free_balance(101), 2000);
		let nominated_value = exposure.others.iter().find(|o| o.who == 101).unwrap().value;

		on_offence_now(
			&[
				OffenceDetails {
					offender: (11, Staking::eras_stakers(Staking::active_era().unwrap().index, 11)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(10)],
		);

		assert_eq!(Balances::free_balance(11), 1000);
		assert_eq!(Balances::free_balance(101), 2000);

		mock::start_era(2);

		assert_eq!(Balances::free_balance(11), 1000);
		assert_eq!(Balances::free_balance(101), 2000);

		mock::start_era(3);

		assert_eq!(Balances::free_balance(11), 1000);
		assert_eq!(Balances::free_balance(101), 2000);

		// at the start of era 4, slashes from era 1 are processed,
		// after being deferred for at least 2 full eras.
		mock::start_era(4);

		assert_eq!(Balances::free_balance(11), 900);
		assert_eq!(Balances::free_balance(101), 2000 - (nominated_value / 10));
	})
}

#[test]
fn remove_deferred() {
	ExtBuilder::default().slash_defer_duration(2).build_and_execute(|| {
		mock::start_era(1);

		assert_eq!(Balances::free_balance(11), 1000);

		let exposure = Staking::eras_stakers(Staking::active_era().unwrap().index, 11);
		assert_eq!(Balances::free_balance(101), 2000);
		let nominated_value = exposure.others.iter().find(|o| o.who == 101).unwrap().value;

		on_offence_now(
			&[
				OffenceDetails {
					offender: (11, exposure.clone()),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(10)],
		);

		assert_eq!(Balances::free_balance(11), 1000);
		assert_eq!(Balances::free_balance(101), 2000);

		mock::start_era(2);

		on_offence_in_era(
			&[
				OffenceDetails {
					offender: (11, exposure.clone()),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(15)],
			1,
		);

		// fails if empty
		assert_noop!(
			Staking::cancel_deferred_slash(Origin::ROOT, 1, vec![]),
			Error::<Test>::EmptyTargets
		);

		assert_ok!(Staking::cancel_deferred_slash(Origin::ROOT, 1, vec![0]));

		assert_eq!(Balances::free_balance(11), 1000);
		assert_eq!(Balances::free_balance(101), 2000);

		mock::start_era(3);

		assert_eq!(Balances::free_balance(11), 1000);
		assert_eq!(Balances::free_balance(101), 2000);

		// at the start of era 4, slashes from era 1 are processed,
		// after being deferred for at least 2 full eras.
		mock::start_era(4);

		// the first slash for 10% was cancelled, so no effect.
		assert_eq!(Balances::free_balance(11), 1000);
		assert_eq!(Balances::free_balance(101), 2000);

		mock::start_era(5);

		let slash_10 = Perbill::from_percent(10);
		let slash_15 = Perbill::from_percent(15);
		let initial_slash = slash_10 * nominated_value;

		let total_slash = slash_15 * nominated_value;
		let actual_slash = total_slash - initial_slash;

		// 5% slash (15 - 10) processed now.
		assert_eq!(Balances::free_balance(11), 950);
		assert_eq!(Balances::free_balance(101), 2000 - actual_slash);
	})
}

#[test]
fn remove_multi_deferred() {
	ExtBuilder::default().slash_defer_duration(2).build_and_execute(|| {
		mock::start_era(1);

		assert_eq!(Balances::free_balance(11), 1000);

		let exposure = Staking::eras_stakers(Staking::active_era().unwrap().index, 11);
		assert_eq!(Balances::free_balance(101), 2000);

		on_offence_now(
			&[
				OffenceDetails {
					offender: (11, exposure.clone()),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(10)],
		);

		on_offence_now(
			&[
				OffenceDetails {
					offender: (21, Staking::eras_stakers(Staking::active_era().unwrap().index, 21)),
					reporters: vec![],
				}
			],
			&[Perbill::from_percent(10)],
		);

		on_offence_now(
			&[
				OffenceDetails {
					offender: (11, exposure.clone()),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(25)],
		);

		on_offence_now(
			&[
				OffenceDetails {
					offender: (42, exposure.clone()),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(25)],
		);

		on_offence_now(
			&[
				OffenceDetails {
					offender: (69, exposure.clone()),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(25)],
		);

		assert_eq!(<Staking as Store>::UnappliedSlashes::get(&1).len(), 5);

		// fails if list is not sorted
		assert_noop!(
			Staking::cancel_deferred_slash(Origin::ROOT, 1, vec![2, 0, 4]),
			Error::<Test>::NotSortedAndUnique
		);
		// fails if list is not unique
		assert_noop!(
			Staking::cancel_deferred_slash(Origin::ROOT, 1, vec![0, 2, 2]),
			Error::<Test>::NotSortedAndUnique
		);
		// fails if bad index
		assert_noop!(
			Staking::cancel_deferred_slash(Origin::ROOT, 1, vec![1, 2, 3, 4, 5]),
			Error::<Test>::InvalidSlashIndex
		);

		assert_ok!(Staking::cancel_deferred_slash(Origin::ROOT, 1, vec![0, 2, 4]));

		let slashes = <Staking as Store>::UnappliedSlashes::get(&1);
		assert_eq!(slashes.len(), 2);
		assert_eq!(slashes[0].validator, 21);
		assert_eq!(slashes[1].validator, 42);
	})
}

mod offchain_phragmen {
	use crate::*;
	use frame_support::{assert_noop, assert_ok};
	use sp_runtime::transaction_validity::TransactionSource;
	use mock::*;
	use parking_lot::RwLock;
	use sp_core::offchain::{
		testing::{PoolState, TestOffchainExt, TestTransactionPoolExt},
		OffchainExt, TransactionPoolExt,
	};
	use sp_io::TestExternalities;
	use sp_phragmen::StakedAssignment;
	use frame_support::traits::OffchainWorker;
	use std::sync::Arc;
	use substrate_test_utils::assert_eq_uvec;

	fn percent(x: u16) -> OffchainAccuracy {
		OffchainAccuracy::from_percent(x)
	}

	/// setup a new set of validators and nominator storage items independent of the parent mock
	/// file. This produces a edge graph that can be reduced.
	fn build_offchain_phragmen_test_ext() {
		for i in (10..=40).step_by(10) {
			// Note: we respect the convention of the mock (10, 11 pairs etc.) since these accounts
			// have corresponding keys in session which makes everything more ergonomic and
			// realistic.
			bond_validator(i + 1, i, 100);
		}

		let mut voter = 1;
		bond_nominator(voter, 1000 + voter, 100, vec![11]);
		voter = 2;
		bond_nominator(voter, 1000 + voter, 100, vec![11, 11]);
		voter = 3;
		bond_nominator(voter, 1000 + voter, 100, vec![21, 41]);
		voter = 4;
		bond_nominator(voter, 1000 + voter, 100, vec![21, 31, 41]);
		voter = 5;
		bond_nominator(voter, 1000 + voter, 100, vec![21, 31, 41]);
	}

	fn offchainify(ext: &mut TestExternalities) -> Arc<RwLock<PoolState>> {
		let (offchain, _state) = TestOffchainExt::new();
		let (pool, state) = TestTransactionPoolExt::new();

		ext.register_extension(OffchainExt::new(offchain));
		ext.register_extension(TransactionPoolExt::new(pool));

		state
	}

	#[test]
	fn is_current_session_final_works() {
		ExtBuilder::default()
			.session_per_era(3)
			.build()
			.execute_with(|| {
				mock::start_era(1);
				assert_eq!(Session::current_index(), 3);
				assert_eq!(Staking::current_era(), Some(1));
				assert_eq!(Staking::is_current_session_final(), false);

				start_session(4);
				assert_eq!(Session::current_index(), 4);
				assert_eq!(Staking::current_era(), Some(1));
				assert_eq!(Staking::is_current_session_final(), true);

				start_session(5);
				assert_eq!(Session::current_index(), 5);
				// era changed.
				assert_eq!(Staking::current_era(), Some(2));
				assert_eq!(Staking::is_current_session_final(), false);
			})
	}

	#[test]
	fn offchain_election_flag_is_triggered() {
		ExtBuilder::default()
			.session_per_era(5)
			.session_length(10)
			.election_lookahead(3)
			.build()
			.execute_with(|| {
				run_to_block(7);
				assert_session_era!(0, 0);

				run_to_block(10);
				assert_session_era!(1, 0);
				assert_eq!(Staking::era_election_status(), ElectionStatus::Closed);
				assert!(Staking::snapshot_nominators().is_none());
				assert!(Staking::snapshot_validators().is_none());

				run_to_block(36);
				assert_session_era!(3, 0);

				// fist era has session 0, which has 0 blocks length, so we have in total 40 blocks
				// in the era.
				run_to_block(37);
				assert_session_era!(3, 0);
				assert_eq!(Staking::era_election_status(), ElectionStatus::Open(37));
				assert!(Staking::snapshot_nominators().is_some());
				assert!(Staking::snapshot_validators().is_some());

				run_to_block(38);
				assert_eq!(Staking::era_election_status(), ElectionStatus::Open(37));

				run_to_block(39);
				assert_eq!(Staking::era_election_status(), ElectionStatus::Open(37));

				run_to_block(40);
				assert_session_era!(4, 0);
				assert_eq!(Staking::era_election_status(), ElectionStatus::Closed);
				assert!(Staking::snapshot_nominators().is_none());
				assert!(Staking::snapshot_validators().is_none());

				run_to_block(86);
				assert_session_era!(8, 1);
				assert_eq!(Staking::era_election_status(), ElectionStatus::Closed);
				assert!(Staking::snapshot_nominators().is_none());
				assert!(Staking::snapshot_validators().is_none());

				// second era onwards has 50 blocks per era.
				run_to_block(87);
				assert_eq!(Staking::era_election_status(), ElectionStatus::Open(87));
				assert!(Staking::snapshot_nominators().is_some());
				assert!(Staking::snapshot_validators().is_some());

				run_to_block(90);
				assert_session_era!(9, 1);
				assert_eq!(Staking::era_election_status(), ElectionStatus::Closed);
				assert!(Staking::snapshot_nominators().is_none());
				assert!(Staking::snapshot_validators().is_none());
			})
	}

	#[test]
	fn offchain_election_flag_is_triggered_when_forcing() {
		ExtBuilder::default()
			.session_per_era(5)
			.session_length(10)
			.election_lookahead(3)
			.build()
			.execute_with(|| {
				run_to_block(7);
				assert_session_era!(0, 0);

				run_to_block(12);
				ForceEra::put(Forcing::ForceNew);
				run_to_block(13);
				assert_eq!(Staking::era_election_status(), ElectionStatus::Closed);

				run_to_block(17); // instead of 47
				assert_eq!(Staking::era_election_status(), ElectionStatus::Open(17));
			})
	}

	#[test]
	fn election_on_chain_fallback_works() {
		ExtBuilder::default().build_and_execute(|| {
			start_session(1);
			start_session(2);
			assert_eq!(Staking::era_election_status(), ElectionStatus::Closed);
			// some election must have happened by now.
			assert_eq!(
				System::events()
					.into_iter()
					.map(|r| r.event)
					.filter_map(|e| {
						if let MetaEvent::staking(inner) = e {
							Some(inner)
						} else {
							None
						}
					})
					.last()
					.unwrap(),
				RawEvent::StakingElection(ElectionCompute::OnChain),
			);
		})
	}

	#[test]
	#[ignore] // This takes a few mins
	fn offchain_wont_work_if_snapshot_fails() {
		ExtBuilder::default()
			.offchain_phragmen_ext()
			.build()
			.execute_with(|| {
				run_to_block(12);
				assert!(Staking::snapshot_validators().is_some());
				assert_eq!(Staking::era_election_status(), ElectionStatus::Open(12));

				// validate more than the limit
				let limit: NominatorIndex = ValidatorIndex::max_value() as NominatorIndex + 1;
				let ctrl = 1_000_000;
				for i in 0..limit {
					bond_validator((1000 + i).into(), (1000 + i + ctrl).into(), 100);
				}

				// window stays closed since no snapshot was taken.
				run_to_block(27);
				assert!(Staking::snapshot_validators().is_none());
				assert_eq!(Staking::era_election_status(), ElectionStatus::Closed);
			})
	}

	#[test]
	fn staking_is_locked_when_election_window_open() {
		ExtBuilder::default()
			.offchain_phragmen_ext()
			.election_lookahead(3)
			.build()
			.execute_with(|| {
				run_to_block(12);
				assert!(Staking::snapshot_validators().is_some());
				// given
				assert_eq!(Staking::era_election_status(), ElectionStatus::Open(12));

				// chill et. al. are now not allowed.
				assert_noop!(
					Staking::chill(Origin::signed(10)),
					Error::<Test>::CallNotAllowed,
				);
			})
	}

	#[test]
	fn signed_result_can_be_submitted() {
		// should check that we have a new validator set normally,
		// event says that it comes from offchain.
		ExtBuilder::default()
			.offchain_phragmen_ext()
			.build()
			.execute_with(|| {
				run_to_block(12);
				assert_eq!(Staking::era_election_status(), ElectionStatus::Open(12));
				assert!(Staking::snapshot_validators().is_some());

				let (compact, winners, score) = prepare_submission_with(true, |_| {});
				assert_ok!(Staking::submit_election_solution(
					Origin::signed(10),
					winners,
					compact,
					score,
					current_era(),
				));

				let queued_result = Staking::queued_elected().unwrap();
				assert_eq!(queued_result.compute, ElectionCompute::Signed);

				run_to_block(15);
				assert_eq!(Staking::era_election_status(), ElectionStatus::Closed);

				assert_eq!(
					System::events()
						.into_iter()
						.map(|r| r.event)
						.filter_map(|e| {
							if let MetaEvent::staking(inner) = e {
								Some(inner)
							} else {
								None
							}
						})
						.last()
						.unwrap(),
					RawEvent::StakingElection(ElectionCompute::Signed),
				);
			})
	}

	#[test]
	fn signed_result_can_be_submitted_later() {
		// same as `signed_result_can_be_submitted` but at a later block.
		ExtBuilder::default()
			.offchain_phragmen_ext()
			.build()
			.execute_with(|| {
				run_to_block(14);
				assert_eq!(Staking::era_election_status(), ElectionStatus::Open(12));

				let (compact, winners, score) = prepare_submission_with(true, |_| {});
				assert_ok!(Staking::submit_election_solution(
					Origin::signed(10),
					winners,
					compact,
					score,
					current_era(),
				));

				let queued_result = Staking::queued_elected().unwrap();
				assert_eq!(queued_result.compute, ElectionCompute::Signed);

				run_to_block(15);
				assert_eq!(Staking::era_election_status(), ElectionStatus::Closed);

				assert_eq!(
					System::events()
						.into_iter()
						.map(|r| r.event)
						.filter_map(|e| {
							if let MetaEvent::staking(inner) = e {
								Some(inner)
							} else {
								None
							}
						})
						.last()
						.unwrap(),
					RawEvent::StakingElection(ElectionCompute::Signed),
				);
			})
	}

	#[test]
	fn early_solution_submission_is_rejected() {
		// should check that we have a new validator set normally,
		// event says that it comes from offchain.
		ExtBuilder::default()
			.offchain_phragmen_ext()
			.build()
			.execute_with(|| {
				run_to_block(11);
				// submission is not yet allowed
				assert_eq!(Staking::era_election_status(), ElectionStatus::Closed);

				// create all the indices just to build the solution.
				Staking::create_stakers_snapshot();
				let (compact, winners, score) = prepare_submission_with(true, |_| {});
				Staking::kill_stakers_snapshot();

				assert_noop!(
					Staking::submit_election_solution(
						Origin::signed(10),
						winners,
						compact,
						score,
						current_era(),
					),
					Error::<Test>::PhragmenEarlySubmission,
				);
			})
	}

	#[test]
	fn weak_solution_is_rejected() {
		// A solution which is weaker than what we currently have on-chain is rejected.
		ExtBuilder::default()
			.offchain_phragmen_ext()
			.has_stakers(false)
			.validator_count(4)
			.build()
			.execute_with(|| {
				build_offchain_phragmen_test_ext();
				run_to_block(12);

				// a good solution
				let (compact, winners, score) = prepare_submission_with(true, |_| {});
				assert_ok!(Staking::submit_election_solution(
					Origin::signed(10),
					winners,
					compact,
					score,
					current_era(),
				));

				// a bad solution
				let (compact, winners, score) = horrible_phragmen_with_post_processing(false);
				assert_noop!(
					Staking::submit_election_solution(
						Origin::signed(10),
						winners,
						compact,
						score,
						current_era(),
					),
					Error::<Test>::PhragmenWeakSubmission,
				);
			})
	}

	#[test]
	fn better_solution_is_accepted() {
		// A solution which is better than what we currently have on-chain is accepted.
		ExtBuilder::default()
			.offchain_phragmen_ext()
			.validator_count(4)
			.has_stakers(false)
			.build()
			.execute_with(|| {
				build_offchain_phragmen_test_ext();
				run_to_block(12);

				// a meeeeh solution
				let (compact, winners, score) = horrible_phragmen_with_post_processing(false);
				assert_ok!(Staking::submit_election_solution(
					Origin::signed(10),
					winners,
					compact,
					score,
					current_era(),
				));

				// a better solution
				let (compact, winners, score) = prepare_submission_with(true, |_| {});
				assert_ok!(Staking::submit_election_solution(
					Origin::signed(10),
					winners,
					compact,
					score,
					current_era(),
				));
			})
	}

	#[test]
	fn offchain_worker_runs_when_window_open() {
		// at the end of the first finalized block with ElectionStatus::open(_), it should execute.
		let mut ext = ExtBuilder::default()
			.offchain_phragmen_ext()
			.validator_count(2)
			.build();
		let state = offchainify(&mut ext);
		ext.execute_with(|| {
			run_to_block(12);

			// local key 11 is in the elected set.
			assert_eq_uvec!(Session::validators(), vec![11, 21]);
			assert_eq!(state.read().transactions.len(), 0);
			Staking::offchain_worker(12);
			assert_eq!(state.read().transactions.len(), 1);

			let encoded = state.read().transactions[0].clone();
			let extrinsic: Extrinsic = Decode::decode(&mut &*encoded).unwrap();

			let call = extrinsic.call;
			let inner = match call {
				mock::Call::Staking(inner) => inner,
			};

			assert_eq!(
				<Staking as sp_runtime::traits::ValidateUnsigned>::validate_unsigned(
					TransactionSource::Local,
					&inner,
				),
				TransactionValidity::Ok(ValidTransaction {
					priority: (1 << 20) + 1125, // the proposed slot stake.
					requires: vec![],
					provides: vec![("StakingOffchain", current_era()).encode()],
					longevity: 3,
					propagate: false,
				})
			)
		})
	}

	#[test]
	fn mediocre_submission_from_authority_is_early_rejected() {
		let mut ext = ExtBuilder::default()
			.offchain_phragmen_ext()
			.validator_count(4)
			.build();
		let state = offchainify(&mut ext);
		ext.execute_with(|| {
			run_to_block(12);
			// put a good solution on-chain
			let (compact, winners, score) = prepare_submission_with(true, |_| {});
			assert_ok!(Staking::submit_election_solution(
				Origin::signed(10),
				winners,
				compact,
				score,
				current_era(),
			),);

			// now run the offchain worker in the same chain state.
			Staking::offchain_worker(12);
			assert_eq!(state.read().transactions.len(), 1);

			let encoded = state.read().transactions[0].clone();
			let extrinsic: Extrinsic = Decode::decode(&mut &*encoded).unwrap();

			let call = extrinsic.call;
			let inner = match call {
				mock::Call::Staking(inner) => inner,
			};

			// pass this call to ValidateUnsigned
			assert_eq!(
				<Staking as sp_runtime::traits::ValidateUnsigned>::validate_unsigned(
					TransactionSource::Local,
					&inner,
				),
				TransactionValidity::Err(
					InvalidTransaction::Custom(<Error<Test>>::PhragmenWeakSubmission.as_u8()).into(),
				),
			)
		})
	}

	#[test]
	fn invalid_phragmen_result_correct_number_of_winners() {
		ExtBuilder::default()
			.offchain_phragmen_ext()
			.validator_count(4)
			.has_stakers(false)
			.build()
			.execute_with(|| {
				build_offchain_phragmen_test_ext();
				run_to_block(12);

				ValidatorCount::put(3);
				let (compact, winners, score) = prepare_submission_with(true, |_| {});
				ValidatorCount::put(4);

				assert_eq!(winners.len(), 3);

				assert_noop!(
					Staking::submit_election_solution(
						Origin::signed(10),
						winners,
						compact,
						score,
						current_era(),
					),
					Error::<Test>::PhragmenBogusWinnerCount,
				);
			})
	}

	#[test]
	fn invalid_phragmen_result_correct_number_of_winners_1() {
		// if we have too little validators, then the number of candidates is the bound.
		ExtBuilder::default()
			.offchain_phragmen_ext()
			.validator_count(8) // we simply cannot elect 8
			.has_stakers(false)
			.build()
			.execute_with(|| {
				build_offchain_phragmen_test_ext();
				run_to_block(12);

				ValidatorCount::put(3);
				let (compact, winners, score) = prepare_submission_with(true, |_| {});
				ValidatorCount::put(4);

				assert_eq!(winners.len(), 3);

				assert_noop!(
					Staking::submit_election_solution(
						Origin::signed(10),
						winners,
						compact,
						score,
						current_era(),
					),
					Error::<Test>::PhragmenBogusWinnerCount,
				);
			})
	}

	#[test]
	fn invalid_phragmen_result_correct_number_of_winners_2() {
		// if we have too little validators, then the number of candidates is the bound.
		ExtBuilder::default()
			.offchain_phragmen_ext()
			.validator_count(8) // we simply cannot elect 8
			.has_stakers(false)
			.build()
			.execute_with(|| {
				build_offchain_phragmen_test_ext();
				run_to_block(12);

				let (compact, winners, score) = prepare_submission_with(true, |_| {});

				assert_eq!(winners.len(), 4);

				// all good. We chose 4 and it works.
				assert_ok!(Staking::submit_election_solution(
					Origin::signed(10),
					winners,
					compact,
					score,
					current_era(),
				),);
			})
	}

	#[test]
	fn invalid_phragmen_result_out_of_bound_nominator_index() {
		// A nominator index which is simply invalid
		ExtBuilder::default()
			.offchain_phragmen_ext()
			.validator_count(4)
			.has_stakers(false)
			.build()
			.execute_with(|| {
				build_offchain_phragmen_test_ext();
				run_to_block(12);

				assert_eq!(Staking::snapshot_nominators().unwrap().len(), 5 + 4);
				assert_eq!(Staking::snapshot_validators().unwrap().len(), 4);
				let (mut compact, winners, score) = prepare_submission_with(true, |_| {});

				// index 9 doesn't exist.
				compact.votes1.push((9, 2));

				// The error type sadly cannot be more specific now.
				assert_noop!(
					Staking::submit_election_solution(
						Origin::signed(10),
						winners,
						compact,
						score,
						current_era(),
					),
					Error::<Test>::PhragmenBogusCompact,
				);
			})
	}

	#[test]
	fn invalid_phragmen_result_out_of_bound_validator_index() {
		// A validator index which is out of bound
		ExtBuilder::default()
			.offchain_phragmen_ext()
			.validator_count(4)
			.has_stakers(false)
			.build()
			.execute_with(|| {
				build_offchain_phragmen_test_ext();
				run_to_block(12);

				assert_eq!(Staking::snapshot_nominators().unwrap().len(), 5 + 4);
				assert_eq!(Staking::snapshot_validators().unwrap().len(), 4);
				let (mut compact, winners, score) = prepare_submission_with(true, |_| {});

				// index 4 doesn't exist.
				compact.votes1.push((3, 4));

				// The error type sadly cannot be more specific now.
				assert_noop!(
					Staking::submit_election_solution(
						Origin::signed(10),
						winners,
						compact,
						score,
						current_era(),
					),
					Error::<Test>::PhragmenBogusCompact,
				);
			})
	}

	#[test]
	fn invalid_phragmen_result_out_of_bound_winner_index() {
		// A winner index which is simply invalid
		ExtBuilder::default()
			.offchain_phragmen_ext()
			.validator_count(4)
			.has_stakers(false)
			.build()
			.execute_with(|| {
				build_offchain_phragmen_test_ext();
				run_to_block(12);

				assert_eq!(Staking::snapshot_nominators().unwrap().len(), 5 + 4);
				assert_eq!(Staking::snapshot_validators().unwrap().len(), 4);
				let (compact, _, score) = prepare_submission_with(true, |_| {});

				// index 4 doesn't exist.
				let winners = vec![0, 1, 2, 4];

				assert_noop!(
					Staking::submit_election_solution(
						Origin::signed(10),
						winners,
						compact,
						score,
						current_era(),
					),
					Error::<Test>::PhragmenBogusWinner,
				);
			})
	}

	#[test]
	fn invalid_phragmen_result_non_winner_validator_index() {
		// An edge that points to a correct validator index who is NOT a winner. This is very
		// similar to the test that raises `PhragmenBogusNomination`.
		ExtBuilder::default()
			.offchain_phragmen_ext()
			.validator_count(2) // we select only 2.
			.has_stakers(false)
			.build()
			.execute_with(|| {
				build_offchain_phragmen_test_ext();
				run_to_block(12);

				assert_eq!(Staking::snapshot_nominators().unwrap().len(), 5 + 4);
				assert_eq!(Staking::snapshot_validators().unwrap().len(), 4);
				let (compact, winners, score) = prepare_submission_with(true, |a| {
					a.iter_mut()
						.find(|x| x.who == 5)
						// all 3 cannot be among the winners. Although, all of them are validator
						// candidates.
						.map(|x| x.distribution = vec![(21, 50), (41, 30), (31, 20)]);
				});

				assert_noop!(
					Staking::submit_election_solution(
						Origin::signed(10),
						winners,
						compact,
						score,
						current_era(),
					),
					Error::<Test>::PhragmenBogusEdge,
				);
			})
	}

	#[test]
	fn invalid_phragmen_result_wrong_self_vote() {
		// A self vote for someone else.
		ExtBuilder::default()
			.offchain_phragmen_ext()
			.validator_count(4)
			.has_stakers(false)
			.build()
			.execute_with(|| {
				build_offchain_phragmen_test_ext();
				run_to_block(12);

				let (compact, winners, score) = prepare_submission_with(true, |a| {
					// mutate a self vote to target someone else. That someone else is still among the
					// winners
					a.iter_mut().find(|x| x.who == 11).map(|x| {
						x.distribution
							.iter_mut()
							.find(|y| y.0 == 11)
							.map(|y| y.0 = 21)
					});
				});

				assert_noop!(
					Staking::submit_election_solution(
						Origin::signed(10),
						winners,
						compact,
						score,
						current_era(),
					),
					Error::<Test>::PhragmenBogusSelfVote,
				);
			})
	}

	#[test]
	fn invalid_phragmen_result_wrong_self_vote_2() {
		// A self validator voting for someone else next to self vote.
		ExtBuilder::default()
			.offchain_phragmen_ext()
			.validator_count(4)
			.has_stakers(false)
			.build()
			.execute_with(|| {
				build_offchain_phragmen_test_ext();
				run_to_block(12);

				let (compact, winners, score) = prepare_submission_with(true, |a| {
					// Remove the self vote.
					a.retain(|x| x.who != 11);
					// add is as a new double vote
					a.push(StakedAssignment {
						who: 11,
						distribution: vec![(11, 50), (21, 50)],
					});
				});

				// This raises score issue.
				assert_noop!(
					Staking::submit_election_solution(
						Origin::signed(10),
						winners,
						compact,
						score,
						current_era(),
					),
					Error::<Test>::PhragmenBogusSelfVote,
				);
			})
	}

	#[test]
	fn invalid_phragmen_result_over_stake() {
		// Someone's edge ratios sums to more than 100%.
		ExtBuilder::default()
			.offchain_phragmen_ext()
			.validator_count(4)
			.has_stakers(false)
			.build()
			.execute_with(|| {
				build_offchain_phragmen_test_ext();
				run_to_block(12);

				// Note: we don't reduce here to be able to tweak votes3. votes3 will vanish if you
				// reduce.
				let (mut compact, winners, score) = prepare_submission_with(false, |_| {});

				if let Some(c) = compact.votes3.iter_mut().find(|x| x.0 == 0) {
					// by default it should have been (0, [(2, 33%), (1, 33%)], 0)
					// now the sum is above 100%
					c.1 = [(2, percent(66)), (1, percent(66))];
				}

				assert_noop!(
					Staking::submit_election_solution(
						Origin::signed(10),
						winners,
						compact,
						score,
						current_era(),
					),
					Error::<Test>::PhragmenBogusCompact,
				);
			})
	}

	#[test]
	fn invalid_phragmen_result_under_stake() {
		// at the time of this writing, we cannot under stake someone. The compact assignment works
		// in a way that some of the stakes are presented by the submitter, and the last one is read
		// from chain by subtracting the rest from total. Hence, the sum is always correct.
		// This test is only here as a demonstration.
	}

	#[test]
	fn invalid_phragmen_result_invalid_target_stealing() {
		// A valid voter who voted for someone who is a candidate, and is a correct winner, but is
		// actually NOT nominated by this nominator.
		ExtBuilder::default()
			.offchain_phragmen_ext()
			.validator_count(4)
			.has_stakers(false)
			.build()
			.execute_with(|| {
				build_offchain_phragmen_test_ext();
				run_to_block(12);

				let (compact, winners, score) = prepare_submission_with(false, |a| {
					// 3 only voted for 20 and 40. We add a fake vote to 30. The stake sum is still
					// correctly 100.
					a.iter_mut()
						.find(|x| x.who == 3)
						.map(|x| x.distribution = vec![(21, 50), (41, 30), (31, 20)]);
				});

				assert_noop!(
					Staking::submit_election_solution(
						Origin::signed(10),
						winners,
						compact,
						score,
						current_era(),
					),
					Error::<Test>::PhragmenBogusNomination,
				);
			})
	}

	#[test]
	fn nomination_slash_filter_is_checked() {
		// If a nominator has voted for someone who has been recently slashed, that particular
		// nomination should be disabled for the upcoming election. A solution must respect this
		// rule.
		ExtBuilder::default()
			.offchain_phragmen_ext()
			.validator_count(4)
			.has_stakers(false)
			.build()
			.execute_with(|| {
				build_offchain_phragmen_test_ext();

				// finalize the round with fallback. This is needed since all nominator submission
				// are in era zero and we want this one to pass with no problems.
				run_to_block(15);

				// go to the next session to trigger mock::start_era and bump the active era
				run_to_block(20);

				// slash 10. This must happen outside of the election window.
				let offender_expo = Staking::eras_stakers(Staking::active_era().unwrap().index, 11);
				on_offence_now(
					&[OffenceDetails {
						offender: (11, offender_expo.clone()),
						reporters: vec![],
					}],
					&[Perbill::from_percent(50)],
				);

				// validate 10 again for the next round. But this guy will not have the votes that
				// it should have had from 1 and 2.
				assert_ok!(Staking::validate(
					Origin::signed(10),
					Default::default()
				));

				// open the election window and create snapshots.
				run_to_block(32);

				// a solution that has been prepared after the slash.
				let (compact, winners, score) = prepare_submission_with(false, |a| {
					// no one is allowed to vote for 10, except for itself.
					a.into_iter()
						.filter(|s| s.who != 11)
						.for_each(|s|
							assert!(s.distribution.iter().find(|(t, _)| *t == 11).is_none())
						);
				});

				// can be submitted.
				assert_ok!(Staking::submit_election_solution(
					Origin::signed(10),
					winners,
					compact,
					score,
					current_era(),
				));

				// a wrong solution.
				let (compact, winners, score) = prepare_submission_with(false, |a| {
					// add back the vote that has been filtered out.
					a.push(StakedAssignment {
						who: 1,
						distribution: vec![(11, 100)]
					});
				});

				// is rejected.
				assert_noop!(
					Staking::submit_election_solution(
						Origin::signed(10),
						winners,
						compact,
						score,
						current_era(),
					),
					Error::<Test>::PhragmenSlashedNomination,
				);
			})
	}

	#[test]
	fn invalid_phragmen_result_wrong_score() {
		// A valid voter who's total distributed stake is more than what they bond
		ExtBuilder::default()
			.offchain_phragmen_ext()
			.validator_count(4)
			.has_stakers(false)
			.build()
			.execute_with(|| {
				build_offchain_phragmen_test_ext();
				run_to_block(12);

				let (compact, winners, mut score) = prepare_submission_with(true, |_| {});
				score[0] += 1;

				assert_noop!(
					Staking::submit_election_solution(
						Origin::signed(10),
						winners,
						compact,
						score,
						current_era(),
					),
					Error::<Test>::PhragmenBogusScore,
				);
			})
	}

	#[test]
	fn offchain_storage_is_set() {
		let mut ext = ExtBuilder::default()
			.offchain_phragmen_ext()
			.validator_count(4)
			.build();
		let state = offchainify(&mut ext);

		ext.execute_with(|| {
			use offchain_election::OFFCHAIN_HEAD_DB;
			use sp_runtime::offchain::storage::StorageValueRef;

			run_to_block(12);

			Staking::offchain_worker(12);
			// it works
			assert_eq!(state.read().transactions.len(), 1);

			// and it is set
			let storage = StorageValueRef::persistent(&OFFCHAIN_HEAD_DB);
			assert_eq!(storage.get::<BlockNumber>().unwrap().unwrap(), 12);
		})
	}

	#[test]
	fn offchain_storage_prevents_duplicate() {
		let mut ext = ExtBuilder::default()
			.offchain_phragmen_ext()
			.validator_count(4)
			.build();
		let _ = offchainify(&mut ext);

		ext.execute_with(|| {
			use offchain_election::OFFCHAIN_HEAD_DB;
			use sp_runtime::offchain::storage::StorageValueRef;
			let storage = StorageValueRef::persistent(&OFFCHAIN_HEAD_DB);

			run_to_block(12);

			// first run -- ok
			assert_eq!(
				offchain_election::set_check_offchain_execution_status::<Test>(12),
				Ok(()),
			);
			assert_eq!(storage.get::<BlockNumber>().unwrap().unwrap(), 12);

			// re-execute after the next. not allowed.
			assert_eq!(
				offchain_election::set_check_offchain_execution_status::<Test>(13),
				Err("recently executed."),
			);

			// a fork like situation -- re-execute 10, 11, 12. But it won't go through.
			assert_eq!(
				offchain_election::set_check_offchain_execution_status::<Test>(10),
				Err("fork."),
			);
			assert_eq!(
				offchain_election::set_check_offchain_execution_status::<Test>(11),
				Err("fork."),
			);
			assert_eq!(
				offchain_election::set_check_offchain_execution_status::<Test>(12),
				Err("recently executed."),
			);
		})
	}

	#[test]
	#[should_panic]
	fn offence_is_blocked_when_window_open() {
		ExtBuilder::default()
			.offchain_phragmen_ext()
			.validator_count(4)
			.has_stakers(false)
			.build()
			.execute_with(|| {
				run_to_block(12);
				assert_eq!(Staking::era_election_status(), ElectionStatus::Open(12));

				let offender_expo = Staking::eras_stakers(Staking::active_era().unwrap().index, 10);

				// panic from the impl in mock
				on_offence_now(
					&[OffenceDetails {
						offender: (10, offender_expo.clone()),
						reporters: vec![],
					}],
					&[Perbill::from_percent(10)],
				);
			})
	}
}

#[test]
fn slash_kicks_validators_not_nominators_and_disables_nominator_for_kicked_validator() {
	ExtBuilder::default().build_and_execute(|| {
		mock::start_era(1);
		assert_eq_uvec!(Session::validators(), vec![11, 21]);

		// pre-slash balance
		assert_eq!(Balances::free_balance(11), 1000);
		assert_eq!(Balances::free_balance(101), 2000);

		// 11 and 21 both have the support of 100
		let exposure_11 = Staking::eras_stakers(Staking::active_era().unwrap().index, &11);
		let exposure_21 = Staking::eras_stakers(Staking::active_era().unwrap().index, &21);

		assert_eq!(exposure_11.total, 1000 + 125);
		assert_eq!(exposure_21.total, 1000 + 375);

		on_offence_now(
			&[OffenceDetails {
				offender: (11, exposure_11.clone()),
				reporters: vec![],
			}],
			&[Perbill::from_percent(10)],
		);

		// post-slash balance
		let nominator_slash_amount_11 = 125 / 10;
		assert_eq!(Balances::free_balance(11), 900);
		assert_eq!(
			Balances::free_balance(101),
			2000 - nominator_slash_amount_11
		);

		// This is the best way to check that the validator was chilled; `get` will
		// return default value.
		for (stash, _) in <Staking as Store>::Validators::iter() {
			assert!(stash != 11);
		}

		let nominations = <Staking as Store>::Nominators::get(&101).unwrap();

		// and make sure that the vote will be ignored even if the validator
		// re-registers.
		let last_slash = <Staking as Store>::SlashingSpans::get(&11)
			.unwrap()
			.last_nonzero_slash();
		assert!(nominations.submitted_in < last_slash);

		// actually re-bond the slashed validator
		assert_ok!(Staking::validate(Origin::signed(10), Default::default()));

		mock::start_era(2);
		let exposure_11 = Staking::eras_stakers(Staking::active_era().unwrap().index, &11);
		let exposure_21 = Staking::eras_stakers(Staking::active_era().unwrap().index, &21);

		// 10 is re-elected, but without the support of 100
		assert_eq!(exposure_11.total, 900);

		// 20 is re-elected, with the (almost) entire support of 100
		assert_eq!(exposure_21.total, 1000 + 500 - nominator_slash_amount_11);
	});
}

#[test]
fn claim_reward_at_the_last_era_and_no_double_claim_and_invalid_claim() {
	// should check that:
	// * rewards get paid until history_depth for both validators and nominators
	// * an invalid era to claim doesn't update last_reward
	// * double claim of one era fails
	ExtBuilder::default().nominate(true).build_and_execute(|| {
		let init_balance_10 = Balances::total_balance(&10);
		let init_balance_100 = Balances::total_balance(&100);

		let part_for_10 = Perbill::from_rational_approximation::<u32>(1000, 1125);
		let part_for_100 = Perbill::from_rational_approximation::<u32>(125, 1125);

		// Check state
		Payee::<Test>::insert(11, RewardDestination::Controller);
		Payee::<Test>::insert(101, RewardDestination::Controller);

		<Module<Test>>::reward_by_ids(vec![(11, 1)]);
		// Compute total payout now for whole duration as other parameter won't change
		let total_payout_0 = current_total_payout_for_duration(3000);
		assert!(total_payout_0 > 10); // Test is meaningful if reward something

		mock::start_era(1);

		<Module<Test>>::reward_by_ids(vec![(11, 1)]);
		// Change total issuance in order to modify total payout
		let _ = Balances::deposit_creating(&999, 1_000_000_000);
		// Compute total payout now for whole duration as other parameter won't change
		let total_payout_1 = current_total_payout_for_duration(3000);
		assert!(total_payout_1 > 10); // Test is meaningful if reward something
		assert!(total_payout_1 != total_payout_0);

		mock::start_era(2);

		<Module<Test>>::reward_by_ids(vec![(11, 1)]);
		// Change total issuance in order to modify total payout
		let _ = Balances::deposit_creating(&999, 1_000_000_000);
		// Compute total payout now for whole duration as other parameter won't change
		let total_payout_2 = current_total_payout_for_duration(3000);
		assert!(total_payout_2 > 10); // Test is meaningful if reward something
		assert!(total_payout_2 != total_payout_0);
		assert!(total_payout_2 != total_payout_1);

		mock::start_era(Staking::history_depth() + 1);

		let active_era = Staking::active_era().unwrap().index;

		// This is the latest planned era in staking, not the active era
		let current_era = Staking::current_era().unwrap();

		// Last kept is 1:
		assert!(current_era - Staking::history_depth() == 1);
		assert_noop!(
			Staking::payout_stakers(Origin::signed(1337), 11, 0),
			// Fail: Era out of history
			Error::<Test>::InvalidEraToReward
		);
		assert_ok!(Staking::payout_stakers(Origin::signed(1337), 11, 1));
		assert_ok!(Staking::payout_stakers(Origin::signed(1337), 11, 2));
		assert_noop!(
			Staking::payout_stakers(Origin::signed(1337), 11, 2),
			// Fail: Double claim
			Error::<Test>::AlreadyClaimed
		);
		assert_noop!(
			Staking::payout_stakers(Origin::signed(1337), 11, active_era),
			// Fail: Era not finished yet
			Error::<Test>::InvalidEraToReward
		);

		// Era 0 can't be rewarded anymore and current era can't be rewarded yet
		// only era 1 and 2 can be rewarded.

		assert_eq!(
			Balances::total_balance(&10),
			init_balance_10 + part_for_10 * (total_payout_1 + total_payout_2),
		);
		assert_eq!(
			Balances::total_balance(&100),
			init_balance_100 + part_for_100 * (total_payout_1 + total_payout_2),
		);
	});
}

#[test]
fn zero_slash_keeps_nominators() {
	ExtBuilder::default().build_and_execute(|| {
		mock::start_era(1);

		assert_eq!(Balances::free_balance(11), 1000);

		let exposure = Staking::eras_stakers(Staking::active_era().unwrap().index, 11);
		assert_eq!(Balances::free_balance(101), 2000);

		on_offence_now(
			&[
				OffenceDetails {
					offender: (11, exposure.clone()),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(0)],
		);

		assert_eq!(Balances::free_balance(11), 1000);
		assert_eq!(Balances::free_balance(101), 2000);

		// This is the best way to check that the validator was chilled; `get` will
		// return default value.
		for (stash, _) in <Staking as Store>::Validators::iter() {
			assert!(stash != 11);
		}

		let nominations = <Staking as Store>::Nominators::get(&101).unwrap();

		// and make sure that the vote will not be ignored, because the slash was
		// zero.
		let last_slash = <Staking as Store>::SlashingSpans::get(&11).unwrap().last_nonzero_slash();
		assert!(nominations.submitted_in >= last_slash);
	});
}

#[test]
fn six_session_delay() {
	ExtBuilder::default().build_and_execute(|| {
		use pallet_session::SessionManager;

		let val_set = Session::validators();
		let init_session = Session::current_index();
		let init_active_era = Staking::active_era().unwrap().index;
		// pallet-session is delaying session by one, thus the next session to plan is +2.
		assert_eq!(<Staking as SessionManager<_>>::new_session(init_session + 2), None);
		assert_eq!(<Staking as SessionManager<_>>::new_session(init_session + 3), Some(val_set.clone()));
		assert_eq!(<Staking as SessionManager<_>>::new_session(init_session + 4), None);
		assert_eq!(<Staking as SessionManager<_>>::new_session(init_session + 5), None);
		assert_eq!(<Staking as SessionManager<_>>::new_session(init_session + 6), Some(val_set.clone()));

		<Staking as SessionManager<_>>::end_session(init_session);
		<Staking as SessionManager<_>>::start_session(init_session + 1);
		assert_eq!(Staking::active_era().unwrap().index, init_active_era);
		<Staking as SessionManager<_>>::end_session(init_session + 1);
		<Staking as SessionManager<_>>::start_session(init_session + 2);
		assert_eq!(Staking::active_era().unwrap().index, init_active_era);

		// Reward current era
		Staking::reward_by_ids(vec![(11, 1)]);

		// New active era is triggered here.
		<Staking as SessionManager<_>>::end_session(init_session + 2);
		<Staking as SessionManager<_>>::start_session(init_session + 3);
		assert_eq!(Staking::active_era().unwrap().index, init_active_era + 1);
		<Staking as SessionManager<_>>::end_session(init_session + 3);
		<Staking as SessionManager<_>>::start_session(init_session + 4);
		assert_eq!(Staking::active_era().unwrap().index, init_active_era + 1);
		<Staking as SessionManager<_>>::end_session(init_session + 4);
		<Staking as SessionManager<_>>::start_session(init_session + 5);
		assert_eq!(Staking::active_era().unwrap().index, init_active_era + 1);

		// Reward current era
		Staking::reward_by_ids(vec![(21, 2)]);

		// New active era is triggered here.
		<Staking as SessionManager<_>>::end_session(init_session + 5);
		<Staking as SessionManager<_>>::start_session(init_session + 6);
		assert_eq!(Staking::active_era().unwrap().index, init_active_era + 2);

		// That reward are correct
		assert_eq!(Staking::eras_reward_points(init_active_era).total, 1);
		assert_eq!(Staking::eras_reward_points(init_active_era + 1).total, 2);
	});
}

#[test]
fn test_max_nominator_rewarded_per_validator_and_cant_steal_someone_else_reward() {
	// Test:
	// * If nominator nomination is below the $MaxNominatorRewardedPerValidator other nominator
	//   then the nominator can't claim its reward
	// * A nominator can't claim another nominator reward
	ExtBuilder::default().build_and_execute(|| {
		for i in 0..=<Test as Trait>::MaxNominatorRewardedPerValidator::get() {
			let stash = 10_000 + i as AccountId;
			let controller = 20_000 + i as AccountId;
			let balance = 10_000 + i as Balance;
			Balances::make_free_balance_be(&stash, balance);
			assert_ok!(
				Staking::bond(
					Origin::signed(stash),
					controller,
					balance,
					RewardDestination::Stash
				)
			);
			assert_ok!(Staking::nominate(Origin::signed(controller), vec![11]));
		}
		mock::start_era(1);

		<Module<Test>>::reward_by_ids(vec![(11, 1)]);
		// Compute total payout now for whole duration as other parameter won't change
		let total_payout_0 = current_total_payout_for_duration(3 * 1000);
		assert!(total_payout_0 > 100); // Test is meaningful if reward something

		mock::start_era(2);
		mock::make_all_reward_payment(1);

		// Assert only nominators from 1 to Max are rewarded
		for i in 0..=<Test as Trait>::MaxNominatorRewardedPerValidator::get() {
			let stash = 10_000 + i as AccountId;
			let balance = 10_000 + i as Balance;
			if stash == 10_000 {
				assert!(Balances::free_balance(&stash) == balance);
			} else {
				assert!(Balances::free_balance(&stash) > balance);
			}
		}
	});
}

#[test]
fn set_history_depth_works() {
	ExtBuilder::default().build_and_execute(|| {
		mock::start_era(10);
		Staking::set_history_depth(Origin::ROOT, 20).unwrap();
		assert!(<Staking as Store>::ErasTotalStake::contains_key(10 - 4));
		assert!(<Staking as Store>::ErasTotalStake::contains_key(10 - 5));
		Staking::set_history_depth(Origin::ROOT, 4).unwrap();
		assert!(<Staking as Store>::ErasTotalStake::contains_key(10 - 4));
		assert!(!<Staking as Store>::ErasTotalStake::contains_key(10 - 5));
		Staking::set_history_depth(Origin::ROOT, 3).unwrap();
		assert!(!<Staking as Store>::ErasTotalStake::contains_key(10 - 4));
		assert!(!<Staking as Store>::ErasTotalStake::contains_key(10 - 5));
		Staking::set_history_depth(Origin::ROOT, 8).unwrap();
		assert!(!<Staking as Store>::ErasTotalStake::contains_key(10 - 4));
		assert!(!<Staking as Store>::ErasTotalStake::contains_key(10 - 5));
	});
}

#[test]
fn test_payout_stakers() {
	// Here we will test validator can set `max_nominators_payout` and it works.
	// We also test that `payout_extra_nominators` works.
	ExtBuilder::default().has_stakers(false).build_and_execute(|| {
		let balance = 1000;
		// Create three validators:
		bond_validator(11, 10, balance); // Default(64)

		// Create nominators, targeting stash of validators
		for i in 0..100 {
			bond_nominator(1000 + i, 100 + i, balance + i as Balance, vec![11]);
		}

		mock::start_era(1);
		Staking::reward_by_ids(vec![(11, 1)]);
		// Compute total payout now for whole duration as other parameter won't change
		let total_payout_0 = current_total_payout_for_duration(3 * 1000);
		assert!(total_payout_0 > 100); // Test is meaningful if reward something
		mock::start_era(2);
		assert_ok!(Staking::payout_stakers(Origin::signed(1337), 11, 1));

		// Top 64 nominators of validator 11 automatically paid out, including the validator
		// Validator payout goes to controller.
		assert!(Balances::free_balance(&10) > balance);
		for i in 36..100 {
			assert!(Balances::free_balance(&(100 + i)) > balance + i as Balance);
		}
		// The bottom 36 do not
		for i in 0..36 {
			assert_eq!(Balances::free_balance(&(100 + i)), balance + i as Balance);
		}

		// We track rewards in `claimed_rewards` vec
		assert_eq!(
			Staking::ledger(&10),
			Some(StakingLedger { stash: 11, total: 1000, active: 1000, unlocking: vec![], claimed_rewards: vec![1] })
		);

		for i in 3..16 {
			Staking::reward_by_ids(vec![(11, 1)]);
			// Compute total payout now for whole duration as other parameter won't change
			let total_payout_0 = current_total_payout_for_duration(3 * 1000);
			assert!(total_payout_0 > 100); // Test is meaningful if reward something
			mock::start_era(i);
			assert_ok!(Staking::payout_stakers(Origin::signed(1337), 11, i - 1));
		}

		// We track rewards in `claimed_rewards` vec
		assert_eq!(
			Staking::ledger(&10),
			Some(StakingLedger { stash: 11, total: 1000, active: 1000, unlocking: vec![], claimed_rewards: (1..=14).collect() })
		);

		for i in 16..100 {
			Staking::reward_by_ids(vec![(11, 1)]);
			// Compute total payout now for whole duration as other parameter won't change
			let total_payout_0 = current_total_payout_for_duration(3 * 1000);
			assert!(total_payout_0 > 100); // Test is meaningful if reward something
			mock::start_era(i);
		}

		// We clean it up as history passes
		assert_ok!(Staking::payout_stakers(Origin::signed(1337), 11, 15));
		assert_ok!(Staking::payout_stakers(Origin::signed(1337), 11, 98));
		assert_eq!(
			Staking::ledger(&10),
			Some(StakingLedger { stash: 11, total: 1000, active: 1000, unlocking: vec![], claimed_rewards: vec![15, 98] })
		);

		// Out of order claims works.
		assert_ok!(Staking::payout_stakers(Origin::signed(1337), 11, 69));
		assert_ok!(Staking::payout_stakers(Origin::signed(1337), 11, 23));
		assert_ok!(Staking::payout_stakers(Origin::signed(1337), 11, 42));
		assert_eq!(
			Staking::ledger(&10),
			Some(StakingLedger { stash: 11, total: 1000, active: 1000, unlocking: vec![], claimed_rewards: vec![15, 23, 42, 69, 98] })
		);
	});
}

#[test]
fn payout_stakers_handles_basic_errors() {
	// Here we will test payouts handle all errors.
	ExtBuilder::default().has_stakers(false).build_and_execute(|| {
		// Same setup as the test above
		let balance = 1000;
		bond_validator(11, 10, balance); // Default(64)

		// Create nominators, targeting stash
		for i in 0..100 {
			bond_nominator(1000 + i, 100 + i, balance + i as Balance, vec![11]);
		}

		mock::start_era(1);
		Staking::reward_by_ids(vec![(11, 1)]);
		// Compute total payout now for whole duration as other parameter won't change
		let total_payout_0 = current_total_payout_for_duration(3 * 1000);
		assert!(total_payout_0 > 100); // Test is meaningful if reward something
		mock::start_era(2);

		// Wrong Era, too big
		assert_noop!(Staking::payout_stakers(Origin::signed(1337), 11, 2), Error::<Test>::InvalidEraToReward);
		// Wrong Staker
		assert_noop!(Staking::payout_stakers(Origin::signed(1337), 10, 1), Error::<Test>::NotStash);

		for i in 3..100 {
			Staking::reward_by_ids(vec![(11, 1)]);
			// Compute total payout now for whole duration as other parameter won't change
			let total_payout_0 = current_total_payout_for_duration(3 * 1000);
			assert!(total_payout_0 > 100); // Test is meaningful if reward something
			mock::start_era(i);
		}
		// We are at era 99, with history depth of 84
		// We should be able to payout era 15 through 98 (84 total eras), but not 14 or 99.
		assert_noop!(Staking::payout_stakers(Origin::signed(1337), 11, 14), Error::<Test>::InvalidEraToReward);
		assert_noop!(Staking::payout_stakers(Origin::signed(1337), 11, 99), Error::<Test>::InvalidEraToReward);
		assert_ok!(Staking::payout_stakers(Origin::signed(1337), 11, 15));
		assert_ok!(Staking::payout_stakers(Origin::signed(1337), 11, 98));

		// Can't claim again
		assert_noop!(Staking::payout_stakers(Origin::signed(1337), 11, 15), Error::<Test>::AlreadyClaimed);
		assert_noop!(Staking::payout_stakers(Origin::signed(1337), 11, 98), Error::<Test>::AlreadyClaimed);
	});
}

#[test]
fn bond_during_era_correctly_populates_claimed_rewards() {
	ExtBuilder::default().has_stakers(false).build_and_execute(|| {
		// Era = None
		bond_validator(9, 8, 1000);
		assert_eq!(
			Staking::ledger(&8),
			Some(StakingLedger {
				stash: 9,
				total: 1000,
				active: 1000,
				unlocking: vec![],
				claimed_rewards: vec![],
			})
		);
		mock::start_era(5);
		bond_validator(11, 10, 1000);
		assert_eq!(
			Staking::ledger(&10),
			Some(StakingLedger {
				stash: 11,
				total: 1000,
				active: 1000,
				unlocking: vec![],
				claimed_rewards: (0..5).collect(),
			})
		);
		mock::start_era(99);
		bond_validator(13, 12, 1000);
		assert_eq!(
			Staking::ledger(&12),
			Some(StakingLedger {
				stash: 13,
				total: 1000,
				active: 1000,
				unlocking: vec![],
				claimed_rewards: (15..99).collect(),
			})
		);
	});
}

/* These migration tests below can be removed once migration code is removed */

#[test]
fn assert_migration_is_noop() {
	let kusama_active_era = "4a0200000190e2721171010000";
	let era = ActiveEraInfo::decode(&mut &hex::decode(kusama_active_era).unwrap()[..]).unwrap();
	assert_eq!(era.index, 586);
	assert_eq!(era.start, Some(1585135674000));
}

#[test]
fn test_last_reward_migration() {
	use sp_storage::Storage;

	let mut s = Storage::default();

	#[derive(PartialEq, Eq, Clone, Encode, Decode, RuntimeDebug)]
	struct OldStakingLedger<AccountId, Balance: HasCompact> {
		pub stash: AccountId,
		#[codec(compact)]
		pub total: Balance,
		#[codec(compact)]
		pub active: Balance,
		pub unlocking: Vec<UnlockChunk<Balance>>,
		pub last_reward: Option<EraIndex>,
	}

	let old_staking10 = OldStakingLedger::<u64, u64> {
		stash: 0,
		total: 10,
		active: 10,
		unlocking: vec![UnlockChunk{ value: 1234, era: 56}],
		last_reward: Some(8),
	};

	let old_staking11 = OldStakingLedger::<u64, u64> {
		stash: 1,
		total: 0,
		active: 0,
		unlocking: vec![],
		last_reward: None,
	};

	let old_staking12 = OldStakingLedger::<u64, u64> {
		stash: 2,
		total: 100,
		active: 100,
		unlocking: vec![UnlockChunk{ value: 9876, era: 54}, UnlockChunk{ value: 98, era: 76}],
		last_reward: Some(23),
	};

	let old_staking13 = OldStakingLedger::<u64, u64> {
		stash: 3,
		total: 100,
		active: 100,
		unlocking: vec![],
		last_reward: Some(23),
	};

	let data = vec![
		(
			Ledger::<Test>::hashed_key_for(10),
			old_staking10.encode().to_vec()
		),
		(
			Ledger::<Test>::hashed_key_for(11),
			old_staking11.encode().to_vec()
		),
		(
			Ledger::<Test>::hashed_key_for(12),
			old_staking12.encode().to_vec()
		),
		(
			Ledger::<Test>::hashed_key_for(13),
			old_staking13.encode().to_vec()
		),
	];

	s.top = data.into_iter().collect();
	sp_io::TestExternalities::new(s).execute_with(|| {
		HistoryDepth::put(84);
		CurrentEra::put(99);
		let nominations = Nominations::<AccountId> {
			targets: vec![],
			submitted_in: 0,
			suppressed: false
		};
		Nominators::<Test>::insert(3, nominations);
		Bonded::<Test>::insert(3, 13);
		Staking::migrate_last_reward_to_claimed_rewards();
		// Test staker out of range
		assert_eq!(
			Ledger::<Test>::get(10),
			Some(StakingLedger {
				stash: 0,
				total: 10,
				active: 10,
				unlocking: vec![UnlockChunk{ value: 1234, era: 56}],
				claimed_rewards: vec![],
			})
		);
		// Test staker none
		assert_eq!(
			Ledger::<Test>::get(11),
			Some(StakingLedger {
				stash: 1,
				total: 0,
				active: 0,
				unlocking: vec![],
				claimed_rewards: vec![],
			})
		);
		// Test staker migration
		assert_eq!(
			Ledger::<Test>::get(12),
			Some(StakingLedger {
				stash: 2,
				total: 100,
				active: 100,
				unlocking: vec![UnlockChunk{ value: 9876, era: 54}, UnlockChunk{ value: 98, era: 76}],
				claimed_rewards: vec![15,16,17,18,19,20,21,22,23],
			})
		);
		// Test nominator migration
		assert_eq!(
			Ledger::<Test>::get(13),
			Some(StakingLedger {
				stash: 3,
				total: 100,
				active: 100,
				unlocking: vec![],
				claimed_rewards: vec![15,16,17,18,19,20,21,22,23],
			})
		);
	});
}

#[test]
fn rewards_should_work_before_migration() {
	// should check that before migration:
	// * rewards get recorded per session
	// * rewards get paid per Era
	// * Check that nominators are also rewarded
	ExtBuilder::default().nominate(true).build_and_execute(|| {
		MigrateEra::put(10);
		let init_balance_10 = Balances::total_balance(&10);
		let init_balance_11 = Balances::total_balance(&11);
		let init_balance_20 = Balances::total_balance(&20);
		let init_balance_21 = Balances::total_balance(&21);
		let init_balance_100 = Balances::total_balance(&100);
		let init_balance_101 = Balances::total_balance(&101);

		// Check state
		Payee::<Test>::insert(11, RewardDestination::Controller);
		Payee::<Test>::insert(21, RewardDestination::Controller);
		Payee::<Test>::insert(101, RewardDestination::Controller);

		<Module<Test>>::reward_by_ids(vec![(11, 50)]);
		<Module<Test>>::reward_by_ids(vec![(11, 50)]);
		// This is the second validator of the current elected set.
		<Module<Test>>::reward_by_ids(vec![(21, 50)]);

		// Compute total payout now for whole duration as other parameter won't change
		let total_payout_0 = current_total_payout_for_duration(3 * 1000);
		assert!(total_payout_0 > 10); // Test is meaningful if reward something

		start_session(1);

		assert_eq!(Balances::total_balance(&10), init_balance_10);
		assert_eq!(Balances::total_balance(&11), init_balance_11);
		assert_eq!(Balances::total_balance(&20), init_balance_20);
		assert_eq!(Balances::total_balance(&21), init_balance_21);
		assert_eq!(Balances::total_balance(&100), init_balance_100);
		assert_eq!(Balances::total_balance(&101), init_balance_101);
		assert_eq_uvec!(Session::validators(), vec![11, 21]);
		assert_eq!(Staking::eras_reward_points(Staking::active_era().unwrap().index), EraRewardPoints {
			total: 50*3,
			individual: vec![(11, 100), (21, 50)].into_iter().collect(),
		});
		let part_for_10 = Perbill::from_rational_approximation::<u32>(1000, 1125);
		let part_for_20 = Perbill::from_rational_approximation::<u32>(1000, 1375);
		let part_for_100_from_10 = Perbill::from_rational_approximation::<u32>(125, 1125);
		let part_for_100_from_20 = Perbill::from_rational_approximation::<u32>(375, 1375);

		start_session(2);
		start_session(3);

		assert_eq!(Staking::active_era().unwrap().index, 1);
		mock::make_all_reward_payment_before_migration(0);

		assert_eq_error_rate!(Balances::total_balance(&10), init_balance_10 + part_for_10 * total_payout_0*2/3, 2);
		assert_eq_error_rate!(Balances::total_balance(&11), init_balance_11, 2);
		assert_eq_error_rate!(Balances::total_balance(&20), init_balance_20 + part_for_20 * total_payout_0*1/3, 2);
		assert_eq_error_rate!(Balances::total_balance(&21), init_balance_21, 2);
		assert_eq_error_rate!(
			Balances::total_balance(&100),
			init_balance_100
				+ part_for_100_from_10 * total_payout_0 * 2/3
				+ part_for_100_from_20 * total_payout_0 * 1/3,
			2
		);
		assert_eq_error_rate!(Balances::total_balance(&101), init_balance_101, 2);

		assert_eq_uvec!(Session::validators(), vec![11, 21]);
		<Module<Test>>::reward_by_ids(vec![(11, 1)]);

		// Compute total payout now for whole duration as other parameter won't change
		let total_payout_1 = current_total_payout_for_duration(3 * 1000);
		assert!(total_payout_1 > 10); // Test is meaningful if reward something

		mock::start_era(2);
		mock::make_all_reward_payment_before_migration(1);

		assert_eq_error_rate!(Balances::total_balance(&10), init_balance_10 + part_for_10 * (total_payout_0 * 2/3 + total_payout_1), 2);
		assert_eq_error_rate!(Balances::total_balance(&11), init_balance_11, 2);
		assert_eq_error_rate!(Balances::total_balance(&20), init_balance_20 + part_for_20 * total_payout_0 * 1/3, 2);
		assert_eq_error_rate!(Balances::total_balance(&21), init_balance_21, 2);
		assert_eq_error_rate!(
			Balances::total_balance(&100),
			init_balance_100
				+ part_for_100_from_10 * (total_payout_0 * 2/3 + total_payout_1)
				+ part_for_100_from_20 * total_payout_0 * 1/3,
			2
		);
		assert_eq_error_rate!(Balances::total_balance(&101), init_balance_101, 2);
	});
}

#[test]
fn migrate_era_should_work() {
	// should check that before and after migration:
	// * rewards get recorded per session
	// * rewards get paid per Era
	// * Check that nominators are also rewarded
	ExtBuilder::default().nominate(true).build_and_execute(|| {
		MigrateEra::put(1);
		let init_balance_10 = Balances::total_balance(&10);
		let init_balance_11 = Balances::total_balance(&11);
		let init_balance_20 = Balances::total_balance(&20);
		let init_balance_21 = Balances::total_balance(&21);
		let init_balance_100 = Balances::total_balance(&100);
		let init_balance_101 = Balances::total_balance(&101);

		// Check state
		Payee::<Test>::insert(11, RewardDestination::Controller);
		Payee::<Test>::insert(21, RewardDestination::Controller);
		Payee::<Test>::insert(101, RewardDestination::Controller);

		<Module<Test>>::reward_by_ids(vec![(11, 50)]);
		<Module<Test>>::reward_by_ids(vec![(11, 50)]);
		// This is the second validator of the current elected set.
		<Module<Test>>::reward_by_ids(vec![(21, 50)]);

		// Compute total payout now for whole duration as other parameter won't change
		let total_payout_0 = current_total_payout_for_duration(3 * 1000);
		assert!(total_payout_0 > 10); // Test is meaningful if reward something

		start_session(1);

		assert_eq!(Balances::total_balance(&10), init_balance_10);
		assert_eq!(Balances::total_balance(&11), init_balance_11);
		assert_eq!(Balances::total_balance(&20), init_balance_20);
		assert_eq!(Balances::total_balance(&21), init_balance_21);
		assert_eq!(Balances::total_balance(&100), init_balance_100);
		assert_eq!(Balances::total_balance(&101), init_balance_101);
		assert_eq_uvec!(Session::validators(), vec![11, 21]);
		assert_eq!(Staking::eras_reward_points(Staking::active_era().unwrap().index), EraRewardPoints {
			total: 50*3,
			individual: vec![(11, 100), (21, 50)].into_iter().collect(),
		});
		let part_for_10 = Perbill::from_rational_approximation::<u32>(1000, 1125);
		let part_for_20 = Perbill::from_rational_approximation::<u32>(1000, 1375);
		let part_for_100_from_10 = Perbill::from_rational_approximation::<u32>(125, 1125);
		let part_for_100_from_20 = Perbill::from_rational_approximation::<u32>(375, 1375);

		start_session(2);
		start_session(3);

		assert_eq!(Staking::active_era().unwrap().index, 1);
		mock::make_all_reward_payment_before_migration(0);

		assert_eq_error_rate!(Balances::total_balance(&10), init_balance_10 + part_for_10 * total_payout_0*2/3, 2);
		assert_eq_error_rate!(Balances::total_balance(&11), init_balance_11, 2);
		assert_eq_error_rate!(Balances::total_balance(&20), init_balance_20 + part_for_20 * total_payout_0*1/3, 2);
		assert_eq_error_rate!(Balances::total_balance(&21), init_balance_21, 2);
		assert_eq_error_rate!(
			Balances::total_balance(&100),
			init_balance_100
				+ part_for_100_from_10 * total_payout_0 * 2/3
				+ part_for_100_from_20 * total_payout_0 * 1/3,
			2
		);
		assert_eq_error_rate!(Balances::total_balance(&101), init_balance_101, 2);

		assert_eq_uvec!(Session::validators(), vec![11, 21]);
		<Module<Test>>::reward_by_ids(vec![(11, 1)]);

		// Compute total payout now for whole duration as other parameter won't change
		let total_payout_1 = current_total_payout_for_duration(3 * 1000);
		assert!(total_payout_1 > 10); // Test is meaningful if reward something

		mock::start_era(2);
		mock::make_all_reward_payment(1);

		assert_eq_error_rate!(Balances::total_balance(&10), init_balance_10 + part_for_10 * (total_payout_0 * 2/3 + total_payout_1), 2);
		assert_eq_error_rate!(Balances::total_balance(&11), init_balance_11, 2);
		assert_eq_error_rate!(Balances::total_balance(&20), init_balance_20 + part_for_20 * total_payout_0 * 1/3, 2);
		assert_eq_error_rate!(Balances::total_balance(&21), init_balance_21, 2);
		assert_eq_error_rate!(
			Balances::total_balance(&100),
			init_balance_100
				+ part_for_100_from_10 * (total_payout_0 * 2/3 + total_payout_1)
				+ part_for_100_from_20 * total_payout_0 * 1/3,
			2
		);
		assert_eq_error_rate!(Balances::total_balance(&101), init_balance_101, 2);
	});
}

#[test]
#[should_panic]
fn migrate_era_should_handle_error() {
	ExtBuilder::default().nominate(true).build_and_execute(|| {
		MigrateEra::put(1);
		let init_balance_10 = Balances::total_balance(&10);
		let init_balance_11 = Balances::total_balance(&11);
		let init_balance_20 = Balances::total_balance(&20);
		let init_balance_21 = Balances::total_balance(&21);
		let init_balance_100 = Balances::total_balance(&100);
		let init_balance_101 = Balances::total_balance(&101);

		// Check state
		Payee::<Test>::insert(11, RewardDestination::Controller);
		Payee::<Test>::insert(21, RewardDestination::Controller);
		Payee::<Test>::insert(101, RewardDestination::Controller);

		<Module<Test>>::reward_by_ids(vec![(11, 50)]);
		<Module<Test>>::reward_by_ids(vec![(11, 50)]);
		// This is the second validator of the current elected set.
		<Module<Test>>::reward_by_ids(vec![(21, 50)]);

		// Compute total payout now for whole duration as other parameter won't change
		let total_payout_0 = current_total_payout_for_duration(3 * 1000);
		assert!(total_payout_0 > 10); // Test is meaningful if reward something

		start_session(1);

		assert_eq!(Balances::total_balance(&10), init_balance_10);
		assert_eq!(Balances::total_balance(&11), init_balance_11);
		assert_eq!(Balances::total_balance(&20), init_balance_20);
		assert_eq!(Balances::total_balance(&21), init_balance_21);
		assert_eq!(Balances::total_balance(&100), init_balance_100);
		assert_eq!(Balances::total_balance(&101), init_balance_101);
		assert_eq_uvec!(Session::validators(), vec![11, 21]);
		assert_eq!(Staking::eras_reward_points(Staking::active_era().unwrap().index), EraRewardPoints {
			total: 50*3,
			individual: vec![(11, 100), (21, 50)].into_iter().collect(),
		});

		start_session(2);
		start_session(3);

		assert_eq!(Staking::active_era().unwrap().index, 1);
		mock::make_all_reward_payment(0);
	});
}

#[test]
#[should_panic]
fn migrate_era_should_handle_errors_2() {
	// should check that before and after migration:
	// * rewards get recorded per session
	// * rewards get paid per Era
	// * Check that nominators are also rewarded
	ExtBuilder::default().nominate(true).build_and_execute(|| {
		MigrateEra::put(1);
		let init_balance_10 = Balances::total_balance(&10);
		let init_balance_11 = Balances::total_balance(&11);
		let init_balance_20 = Balances::total_balance(&20);
		let init_balance_21 = Balances::total_balance(&21);
		let init_balance_100 = Balances::total_balance(&100);
		let init_balance_101 = Balances::total_balance(&101);

		// Check state
		Payee::<Test>::insert(11, RewardDestination::Controller);
		Payee::<Test>::insert(21, RewardDestination::Controller);
		Payee::<Test>::insert(101, RewardDestination::Controller);

		<Module<Test>>::reward_by_ids(vec![(11, 50)]);
		<Module<Test>>::reward_by_ids(vec![(11, 50)]);
		// This is the second validator of the current elected set.
		<Module<Test>>::reward_by_ids(vec![(21, 50)]);

		// Compute total payout now for whole duration as other parameter won't change
		let total_payout_0 = current_total_payout_for_duration(3 * 1000);
		assert!(total_payout_0 > 10); // Test is meaningful if reward something

		start_session(1);

		assert_eq!(Balances::total_balance(&10), init_balance_10);
		assert_eq!(Balances::total_balance(&11), init_balance_11);
		assert_eq!(Balances::total_balance(&20), init_balance_20);
		assert_eq!(Balances::total_balance(&21), init_balance_21);
		assert_eq!(Balances::total_balance(&100), init_balance_100);
		assert_eq!(Balances::total_balance(&101), init_balance_101);
		assert_eq_uvec!(Session::validators(), vec![11, 21]);
		assert_eq!(Staking::eras_reward_points(Staking::active_era().unwrap().index), EraRewardPoints {
			total: 50*3,
			individual: vec![(11, 100), (21, 50)].into_iter().collect(),
		});
		let part_for_10 = Perbill::from_rational_approximation::<u32>(1000, 1125);
		let part_for_20 = Perbill::from_rational_approximation::<u32>(1000, 1375);
		let part_for_100_from_10 = Perbill::from_rational_approximation::<u32>(125, 1125);
		let part_for_100_from_20 = Perbill::from_rational_approximation::<u32>(375, 1375);

		start_session(2);
		start_session(3);

		assert_eq!(Staking::active_era().unwrap().index, 1);
		mock::make_all_reward_payment_before_migration(0);

		assert_eq_error_rate!(Balances::total_balance(&10), init_balance_10 + part_for_10 * total_payout_0*2/3, 2);
		assert_eq_error_rate!(Balances::total_balance(&11), init_balance_11, 2);
		assert_eq_error_rate!(Balances::total_balance(&20), init_balance_20 + part_for_20 * total_payout_0*1/3, 2);
		assert_eq_error_rate!(Balances::total_balance(&21), init_balance_21, 2);
		assert_eq_error_rate!(
			Balances::total_balance(&100),
			init_balance_100
				+ part_for_100_from_10 * total_payout_0 * 2/3
				+ part_for_100_from_20 * total_payout_0 * 1/3,
			2
		);
		assert_eq_error_rate!(Balances::total_balance(&101), init_balance_101, 2);

		assert_eq_uvec!(Session::validators(), vec![11, 21]);
		<Module<Test>>::reward_by_ids(vec![(11, 1)]);

		// Compute total payout now for whole duration as other parameter won't change
		let total_payout_1 = current_total_payout_for_duration(3 * 1000);
		assert!(total_payout_1 > 10); // Test is meaningful if reward something

		mock::start_era(2);
		mock::make_all_reward_payment_before_migration(1);

		assert_eq_error_rate!(Balances::total_balance(&10), init_balance_10 + part_for_10 * (total_payout_0 * 2/3 + total_payout_1), 2);
		assert_eq_error_rate!(Balances::total_balance(&11), init_balance_11, 2);
		assert_eq_error_rate!(Balances::total_balance(&20), init_balance_20 + part_for_20 * total_payout_0 * 1/3, 2);
		assert_eq_error_rate!(Balances::total_balance(&21), init_balance_21, 2);
		assert_eq_error_rate!(
			Balances::total_balance(&100),
			init_balance_100
				+ part_for_100_from_10 * (total_payout_0 * 2/3 + total_payout_1)
				+ part_for_100_from_20 * total_payout_0 * 1/3,
			2
		);
		assert_eq_error_rate!(Balances::total_balance(&101), init_balance_101, 2);
	});
}