// 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 codec::Encode;
use sp_runtime::{assert_eq_error_rate, traits::{OnInitialize, BadOrigin}};
use sp_staking::offence::OffenceDetails;
use frame_support::{
	assert_ok, assert_noop,
	traits::{Currency, ReservableCurrency},
	dispatch::DispatchError, StorageMap,
};
use substrate_test_utils::assert_eq_uvec;

#[test]
fn force_unstake_works() {
	// Verifies initial conditions of mock
	ExtBuilder::default().build().execute_with(|| {
		// 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),
			DispatchError::Module {
				index: 0,
				error: 1,
				message: Some("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().execute_with(|| {
		// 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![] })
		);
		// 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![] })
		);
		// Account 1 does not control any stash
		assert_eq!(Staking::ledger(&1), None);

		// ValidatorPrefs are default
		assert_eq!(<Validators<Test>>::enumerate().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![] })
		);
		assert_eq!(Staking::nominators(101).unwrap().targets, vec![11, 21]);

		assert_eq!(
			Staking::stakers(11),
			Exposure { total: 1125, own: 1000, others: vec![ IndividualExposure { who: 101, value: 125 }] }
		);
		assert_eq!(
			Staking::stakers(21),
			Exposure { total: 1375, own: 1000, others: vec![ IndividualExposure { who: 101, value: 375 }] }
		);
		// initial slot_stake
		assert_eq!(Staking::slot_stake(),  1125);


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

		// Initial Era and session
		assert_eq!(Staking::current_era(), 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);

		// All exposures must be correct.
		check_exposure_all();
		check_nominator_all();
	});
}

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

		assert!(<Validators<Test>>::enumerate().map(|(c, _)| c).collect::<Vec<u64>>().contains(&11));
		// 10 can control 11 who is initially a validator.
		assert_ok!(Staking::chill(Origin::signed(10)));
		assert!(!<Validators<Test>>::enumerate().map(|(c, _)| c).collect::<Vec<u64>>().contains(&11));

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

		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(false).build().execute_with(|| {
		// Init some balances
		let _ = Balances::make_free_balance_be(&2, 500);

		let delay = 1000;
		let init_balance_2 = Balances::total_balance(&2);
		let init_balance_10 = Balances::total_balance(&10);
		let init_balance_11 = Balances::total_balance(&11);

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

		// Initial config should be correct
		assert_eq!(Staking::current_era(), 0);
		assert_eq!(Session::current_index(), 0);

		// Add a dummy nominator.
		//
		// Equal division indicates that the reward will be equally divided among validator and
		// nominator.
		<Stakers<Test>>::insert(&11, Exposure {
			own: 500,
			total: 1000,
			others: vec![IndividualExposure {who: 2, value: 500 }]
		});

		<Payee<Test>>::insert(&2, RewardDestination::Stash);
		assert_eq!(Staking::payee(2), RewardDestination::Stash);
		assert_eq!(Staking::payee(11), RewardDestination::Controller);

		let mut block = 3; // Block 3 => Session 1 => Era 0
		System::set_block_number(block);
		Timestamp::set_timestamp(block * 5000);	// on time.
		Session::on_initialize(System::block_number());
		assert_eq!(Staking::current_era(), 0);
		assert_eq!(Session::current_index(), 1);
		<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)]);
		// This must be no-op as it is not an elected validator.
		<Module<Test>>::reward_by_ids(vec![(1001, 10_000)]);

		// Compute total payout now for whole duration as other parameter won't change
		let total_payout = current_total_payout_for_duration(9 * 5 * 1000);
		assert!(total_payout > 10); // Test is meaningful if reward something

		// No reward yet
		assert_eq!(Balances::total_balance(&2), init_balance_2);
		assert_eq!(Balances::total_balance(&10), init_balance_10);
		assert_eq!(Balances::total_balance(&11), init_balance_11);

		block = 6; // Block 6 => Session 2 => Era 0
		System::set_block_number(block);
		Timestamp::set_timestamp(block * 5000 + delay);	// a little late.
		Session::on_initialize(System::block_number());
		assert_eq!(Staking::current_era(), 0);
		assert_eq!(Session::current_index(), 2);

		block = 9; // Block 9 => Session 3 => Era 1
		System::set_block_number(block);
		Timestamp::set_timestamp(block * 5000);  // back to being on time. no delays
		Session::on_initialize(System::block_number());
		assert_eq!(Staking::current_era(), 1);
		assert_eq!(Session::current_index(), 3);

		// 11 validator has 2/3 of the total rewards and half half for it and its nominator
		assert_eq_error_rate!(Balances::total_balance(&2), init_balance_2 + total_payout / 3, 1);
		assert_eq_error_rate!(Balances::total_balance(&10), init_balance_10 + total_payout / 3, 1);
		assert_eq!(Balances::total_balance(&11), init_balance_11);
	});
}

#[test]
fn multi_era_reward_should_work() {
	// Should check that:
	// The value of current_session_reward is set at the end of each era, based on
	// slot_stake and session_reward.
	ExtBuilder::default().nominate(false).build().execute_with(|| {
		let init_balance_10 = Balances::total_balance(&10);

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

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

		start_session(0);
		start_session(1);
		start_session(2);
		start_session(3);

		assert_eq!(Staking::current_era(), 1);
		assert_eq!(Balances::total_balance(&10), init_balance_10 + total_payout_0);

		start_session(4);

		let total_payout_1 = current_total_payout_for_duration(3000);
		assert!(total_payout_1 > 10); // Test is meaningfull if reward something
		<Module<Test>>::reward_by_ids(vec![(11, 101)]);

		// new era is triggered here.
		start_session(5);

		// pay time
		assert_eq!(Balances::total_balance(&10), init_balance_10 + total_payout_0 + total_payout_1);
	});
}

#[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(|| {
			Timestamp::set_timestamp(1); // Initialize time.

			// 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 1:
			start_session(1);
			// 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 2:
			start_session(2);

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


			// --- Block 3: the validators will now be queued.
			start_session(3);
			assert_eq!(Staking::current_era(), 1);

			// --- Block 4: the validators will now be changed.
			start_session(4);

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

			// --- Block 5: nothing. 4 is still there.
			start_session(5);
			assert_eq_uvec!(validator_controllers(), vec![20, 4]);

			// --- Block 6: 4 will not be a validator.
			start_session(7);
			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![] })
			);
			// e.g. it cannot spend more than 500 that it has free from the total 2000
			assert_noop!(
				Balances::reserve(&3, 501),
				DispatchError::Module {
					index: 0,
					error: 1,
					message: Some("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]);

			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_eq!(Staking::stakers(10).others.len(), 0);
			assert_eq!(Staking::stakers(20).others.len(), 0);
			assert_eq!(Staking::stakers(30).others.len(), 0);
			check_exposure_all();
			check_nominator_all();
		});
}

#[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);

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

			// trigger era
			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 meaningfull if reward something
			<Module<Test>>::reward_by_ids(vec![(41, 1)]);
			<Module<Test>>::reward_by_ids(vec![(31, 1)]);
			<Module<Test>>::reward_by_ids(vec![(21, 10)]); // must be no-op
			<Module<Test>>::reward_by_ids(vec![(11, 10)]); // must be no-op

			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.
			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.

			// total expo of 10, with 1200 coming from nominators (externals), according to phragmen.
			assert_eq!(Staking::stakers(11).own, 1000);
			assert_eq!(Staking::stakers(11).total, 1000 + 800);
			// 2 and 4 supported 10, each with stake 600, according to phragmen.
			assert_eq!(
				Staking::stakers(11).others.iter().map(|e| e.value).collect::<Vec<BalanceOf<Test>>>(),
				vec![400, 400]
			);
			assert_eq!(
				Staking::stakers(11).others.iter().map(|e| e.who).collect::<Vec<u64>>(),
				vec![3, 1]
			);
			// total expo of 20, with 500 coming from nominators (externals), according to phragmen.
			assert_eq!(Staking::stakers(21).own, 1000);
			assert_eq_error_rate!(Staking::stakers(21).total, 1000 + 1200, 2);
			// 2 and 4 supported 20, each with stake 250, according to phragmen.
			assert_eq!(
				Staking::stakers(21).others.iter().map(|e| e.value).collect::<Vec<BalanceOf<Test>>>(),
				vec![600, 600]
			);
			assert_eq!(
				Staking::stakers(21).others.iter().map(|e| e.who).collect::<Vec<u64>>(),
				vec![3, 1]
			);

			// They are not chosen anymore
			assert_eq!(Staking::stakers(31).total, 0);
			assert_eq!(Staking::stakers(41).total, 0);

			// the total reward for era 1
			let total_payout_1 = current_total_payout_for_duration(3000);
			assert!(total_payout_1 > 100); // Test is meaningfull if reward something
			<Module<Test>>::reward_by_ids(vec![(41, 10)]); // must be no-op
			<Module<Test>>::reward_by_ids(vec![(31, 10)]); // must be no-op
			<Module<Test>>::reward_by_ids(vec![(21, 2)]);
			<Module<Test>>::reward_by_ids(vec![(11, 1)]);

			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

			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,
			);

			check_exposure_all();
			check_nominator_all();
		});
}

#[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().execute_with(|| {
		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 meaningfull if reward something
		<Module<Test>>::reward_by_ids(vec![(11, 1)]);

		// new era, pay rewards,
		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::stakers(&11),
				),
				reporters: vec![],
			}],
			&[Perbill::from_percent(5)],
		);
		let expo = Staking::stakers(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);
		check_exposure_all();
		check_nominator_all();
		// 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().execute_with(|| {
		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().execute_with(|| {
		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().execute_with(|| {
		assert_eq!(Staking::current_era(), 0);

		// Block 1: No change.
		start_session(0);
		assert_eq!(Session::current_index(), 1);
		assert_eq!(Staking::current_era(), 0);

		// Block 2: Simple era change.
		start_session(2);
		assert_eq!(Session::current_index(), 3);
		assert_eq!(Staking::current_era(), 1);

		// Block 3: Schedule an era length change; no visible changes.
		start_session(3);
		assert_eq!(Session::current_index(), 4);
		assert_eq!(Staking::current_era(), 1);

		// Block 4: Era change kicks in.
		start_session(5);
		assert_eq!(Session::current_index(), 6);
		assert_eq!(Staking::current_era(), 2);

		// Block 5: No change.
		start_session(6);
		assert_eq!(Session::current_index(), 7);
		assert_eq!(Staking::current_era(), 2);

		// Block 6: No change.
		start_session(7);
		assert_eq!(Session::current_index(), 8);
		assert_eq!(Staking::current_era(), 2);

		// Block 7: Era increment.
		start_session(8);
		assert_eq!(Session::current_index(), 9);
		assert_eq!(Staking::current_era(), 3);
	});
}

#[test]
fn forcing_new_era_works() {
	ExtBuilder::default().build().execute_with(|| {
		// normal flow of session.
		assert_eq!(Staking::current_era(), 0);
		start_session(0);
		assert_eq!(Staking::current_era(), 0);
		start_session(1);
		assert_eq!(Staking::current_era(), 0);
		start_session(2);
		assert_eq!(Staking::current_era(), 1);

		// no era change.
		ForceEra::put(Forcing::ForceNone);
		start_session(3);
		assert_eq!(Staking::current_era(), 1);
		start_session(4);
		assert_eq!(Staking::current_era(), 1);
		start_session(5);
		assert_eq!(Staking::current_era(), 1);
		start_session(6);
		assert_eq!(Staking::current_era(), 1);

		// back to normal.
		// this immediately starts a new session.
		ForceEra::put(Forcing::NotForcing);
		start_session(7);
		assert_eq!(Staking::current_era(), 2);
		start_session(8);
		assert_eq!(Staking::current_era(), 2);

		// forceful change
		ForceEra::put(Forcing::ForceAlways);
		start_session(9);
		assert_eq!(Staking::current_era(), 3);
		start_session(10);
		assert_eq!(Staking::current_era(), 4);
		start_session(11);
		assert_eq!(Staking::current_era(), 5);

		// just one forceful change
		ForceEra::put(Forcing::ForceNew);
		start_session(12);
		assert_eq!(Staking::current_era(), 6);

		assert_eq!(ForceEra::get(), Forcing::NotForcing);
		start_session(13);
		assert_eq!(Staking::current_era(), 6);

	});
}

#[test]
fn cannot_transfer_staked_balance() {
	// Tests that a stash account cannot transfer funds
	ExtBuilder::default().nominate(false).build().execute_with(|| {
		// 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::stakers(&11).total, 1000);
		// Confirm account 11 cannot transfer as a result
		assert_noop!(
			Balances::transfer(Origin::signed(11), 20, 1),
			DispatchError::Module {
				index: 0,
				error: 1,
				message: Some("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().execute_with(|| {
		// 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::stakers(&21).total, 1000);
		// Confirm account 21 can transfer at most 1000
		assert_noop!(
			Balances::transfer(Origin::signed(21), 20, 1001),
			DispatchError::Module {
				index: 0,
				error: 1,
				message: Some("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().execute_with(|| {
		// 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::stakers(&11).own, 1000);
		// Confirm account 11 cannot transfer as a result
		assert_noop!(
			Balances::reserve(&11, 1),
			DispatchError::Module {
				index: 0,
				error: 1,
				message: Some("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().execute_with(|| {
		// Check that account 11 is a validator
		assert!(Staking::current_elected().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![],
		}));

		// 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 meaningfull if reward something
		<Module<Test>>::reward_by_ids(vec![(11, 1)]);

		start_era(1);

		// 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![],
		}));

		//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 meaningfull if reward something
		<Module<Test>>::reward_by_ids(vec![(11, 1)]);

		start_era(2);

		// 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![],
		}));

		// 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 meaningfull if reward something
		<Module<Test>>::reward_by_ids(vec![(11, 1)]);

		start_era(3);

		// 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![],
		}));
		// 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().execute_with(|| {
		// Initial config
		let stash_initial_balance = Balances::total_balance(&11);

		// check the balance of a validator accounts.
		assert_eq!(Balances::total_balance(&10), 1);
		// check the balance of a validator's stash accounts.
		assert_eq!(Balances::total_balance(&11), stash_initial_balance);
		// and the nominator (to-be)
		let _ = Balances::make_free_balance_be(&2, 500);

		// add a dummy nominator.
		<Stakers<Test>>::insert(&11, Exposure {
			own: 500, // equal division indicates that the reward will be equally divided among validator and nominator.
			total: 1000,
			others: vec![IndividualExposure {who: 2, value: 500 }]
		});
		<Payee<Test>>::insert(&2, RewardDestination::Stash);
		<Validators<Test>>::insert(&11, ValidatorPrefs {
			commission: Perbill::from_percent(50),
		});

		// 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 meaningfull if reward something
		<Module<Test>>::reward_by_ids(vec![(11, 1)]);

		start_era(1);

		// whats left to be shared is the sum of 3 rounds minus the validator's cut.
		let shared_cut = total_payout_0 / 2;
		// Validator's payee is Staked account, 11, reward will be paid here.
		assert_eq!(Balances::total_balance(&11), stash_initial_balance + shared_cut / 2 + shared_cut);
		// Controller account will not get any reward.
		assert_eq!(Balances::total_balance(&10), 1);
		// Rest of the reward will be shared and paid to the nominator in stake.
		assert_eq!(Balances::total_balance(&2), 500 + shared_cut / 2);

		check_exposure_all();
		check_nominator_all();
	});

}

#[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().execute_with(|| {
		// Check that account 10 is a validator
		assert!(<Validators<Test>>::exists(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![],
		}));

		// 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![],
		}));

		// Call the bond_extra function with a large number, should handle it
		assert_ok!(Staking::bond_extra(Origin::signed(11), u64::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![],
		}));
	});
}

#[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().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);

		// Initial config should be correct
		assert_eq!(Staking::current_era(), 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.
		start_era(1);

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

		// trigger next era.
		Timestamp::set_timestamp(10);
		start_era(2);
		assert_eq!(Staking::current_era(), 2);

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

		// 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}] }));

		// trigger next era.
		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}] }));

		// trigger next era.
		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![] }));
	})
}

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

		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);

		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.
			start_era(1);

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

			start_era(2);
			assert_eq!(Staking::current_era(), 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
					},]
				})
			);

			// 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![],
				})
			);

			// 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 }],
				})
			);

			// 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 }],
				})
			);

			// 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![]
				})
			);

			// 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 },
					]
				})
			);

			// 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 },
					]
				})
			);
		})
}

#[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.
			start_era(1);

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

			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 },
					]
				})
			);

			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 },
					]
				})
			);

			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 },
					]
				})
			);

			// 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 },
					]
				})
			);
		})
}

#[test]
fn slot_stake_is_least_staked_validator_and_exposure_defines_maximum_punishment() {
	// Test that slot_stake is determined by the least staked validator
	// Test that slot_stake is the maximum punishment that can happen to a validator
	ExtBuilder::default().nominate(false).fair(false).build().execute_with(|| {
		// Confirm validator count is 2
		assert_eq!(Staking::validator_count(), 2);
		// Confirm account 10 and 20 are validators
		assert!(<Validators<Test>>::exists(&11) && <Validators<Test>>::exists(&21));

		assert_eq!(Staking::stakers(&11).total, 1000);
		assert_eq!(Staking::stakers(&21).total, 2000);

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

		// We confirm initialized slot_stake is this value
		assert_eq!(Staking::slot_stake(), Staking::stakers(&11).total);

		// Now lets lower account 20 stake
		<Stakers<Test>>::insert(&21, Exposure { total: 69, own: 69, others: vec![] });
		assert_eq!(Staking::stakers(&21).total, 69);
		<Ledger<Test>>::insert(&20, StakingLedger { stash: 22, total: 69, active: 69, unlocking: 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 meaningfull 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
		start_era(1);

		// -- new balances + reward
		assert_eq!(Staking::stakers(&11).total, 1000 + total_payout_0 / 2);
		assert_eq!(Staking::stakers(&21).total, 69 + total_payout_0 / 2);

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

		// -- slot stake should also be updated.
		assert_eq!(Staking::slot_stake(), 69 + total_payout_0 / 2);

		check_exposure_all();
		check_nominator_all();
	});
}

#[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().execute_with(|| {
		// 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>>::exists(&10));
		assert!(<Bonded<Test>>::exists(&11));
		assert!(<Validators<Test>>::exists(&11));
		assert!(<Payee<Test>>::exists(&11));

		// Reduce free_balance of controller to 0
		let _ = Balances::slash(&10, u64::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>>::exists(&10));
		assert!(<Bonded<Test>>::exists(&11));
		assert!(<Validators<Test>>::exists(&11));
		assert!(<Payee<Test>>::exists(&11));

		// Reduce free_balance of stash to 0
		let _ = Balances::slash(&11, u64::max_value());
		// Check total balance of stash
		assert_eq!(Balances::total_balance(&11), 0);

		// Check storage items do not exist
		assert!(!<Ledger<Test>>::exists(&10));
		assert!(!<Bonded<Test>>::exists(&11));
		assert!(!<Validators<Test>>::exists(&11));
		assert!(!<Nominators<Test>>::exists(&11));
		assert!(!<Payee<Test>>::exists(&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().execute_with(|| {
		// Make 10 a nominator
		assert_ok!(Staking::nominate(Origin::signed(10), vec![20]));
		// Check that account 10 is a nominator
		assert!(<Nominators<Test>>::exists(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>>::exists(&10));
		assert!(<Bonded<Test>>::exists(&11));
		assert!(<Nominators<Test>>::exists(&11));
		assert!(<Payee<Test>>::exists(&11));

		// Reduce free_balance of controller to 0
		let _ = Balances::slash(&10, u64::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>>::exists(&10));
		assert!(<Bonded<Test>>::exists(&11));
		assert!(<Nominators<Test>>::exists(&11));
		assert!(<Payee<Test>>::exists(&11));

		// Reduce free_balance of stash to 0
		let _ = Balances::slash(&11, u64::max_value());
		// Check total balance of stash
		assert_eq!(Balances::total_balance(&11), 0);

		// Check storage items do not exist
		assert!(!<Ledger<Test>>::exists(&10));
		assert!(!<Bonded<Test>>::exists(&11));
		assert!(!<Validators<Test>>::exists(&11));
		assert!(!<Nominators<Test>>::exists(&11));
		assert!(!<Payee<Test>>::exists(&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().execute_with(|| {
		Timestamp::set_timestamp(1); // Initialize time.

		// 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()));

		// new block
		start_session(1);

		// no change
		assert_eq_uvec!(validator_controllers(), vec![20, 10]);

		// new block
		start_session(2);

		// no change
		assert_eq_uvec!(validator_controllers(), vec![20, 10]);

		// new block --> ne era --> new validators
		start_session(3);

		// 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

		start_session(4);
		assert_eq_uvec!(validator_controllers(), vec![6, 10]);

		start_session(5);
		assert_eq_uvec!(validator_controllers(), vec![6, 10]);

		// ne era
		start_session(6);
		assert_eq_uvec!(validator_controllers(), vec![2, 20]);

		check_exposure_all();
		check_nominator_all();
	});
}

#[test]
fn wrong_vote_is_null() {
	ExtBuilder::default().nominate(false).validator_pool(true).build().execute_with(|| {
		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
		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}]
				})
			);

			start_era(1);
			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);

			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_by_slot_stake() {
	// 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()));

			let total_payout_0 = current_total_payout_for_duration(3000);
			assert!(total_payout_0 > 100); // Test is meaningfull if reward something
			reward_all_elected();
			start_era(1);

			// 2 is elected.
			// and fucks up the slot stake.
			assert_eq_uvec!(validator_controllers(), vec![20, 10, 2]);
			assert_eq!(Staking::slot_stake(), 1);

			// 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);

			let total_payout_1 = current_total_payout_for_duration(3000);
			assert!(total_payout_1 > 100); // Test is meaningfull if reward something
			reward_all_elected();
			start_era(2);

			assert_eq_uvec!(validator_controllers(), vec![20, 10, 2]);
			assert_eq!(Staking::slot_stake(), 1);

			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,
			);
			check_exposure_all();
			check_nominator_all();
		});
}

#[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);

			System::set_block_number(1);
			Session::on_initialize(System::block_number());

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

#[test]
fn phragmen_should_not_overflow_validators() {
	ExtBuilder::default().nominate(false).build().execute_with(|| {
		let _ = Staking::chill(Origin::signed(10));
		let _ = Staking::chill(Origin::signed(20));

		bond_validator(2, u64::max_value());
		bond_validator(4, u64::max_value());

		bond_nominator(6, u64::max_value() / 2, vec![3, 5]);
		bond_nominator(8, u64::max_value() / 2, vec![3, 5]);

		start_era(1);

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

		// This test will fail this. Will saturate.
		// check_exposure_all();
		assert_eq!(Staking::stakers(3).total, u64::max_value());
		assert_eq!(Staking::stakers(5).total, u64::max_value());
	})
}

#[test]
fn phragmen_should_not_overflow_nominators() {
	ExtBuilder::default().nominate(false).build().execute_with(|| {
		let _ = Staking::chill(Origin::signed(10));
		let _ = Staking::chill(Origin::signed(20));

		bond_validator(2, u64::max_value() / 2);
		bond_validator(4, u64::max_value() / 2);

		bond_nominator(6, u64::max_value(), vec![3, 5]);
		bond_nominator(8, u64::max_value(), vec![3, 5]);

		start_era(1);

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

		// Saturate.
		assert_eq!(Staking::stakers(3).total, u64::max_value());
		assert_eq!(Staking::stakers(5).total, u64::max_value());
	})
}

#[test]
fn phragmen_should_not_overflow_ultimate() {
	ExtBuilder::default().nominate(false).build().execute_with(|| {
		bond_validator(2, u64::max_value());
		bond_validator(4, u64::max_value());

		bond_nominator(6, u64::max_value(), vec![3, 5]);
		bond_nominator(8, u64::max_value(), vec![3, 5]);

		start_era(1);

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

		// Saturate.
		assert_eq!(Staking::stakers(3).total, u64::max_value());
		assert_eq!(Staking::stakers(5).total, u64::max_value());
	})
}

#[test]
fn reward_validator_slashing_validator_doesnt_overflow() {
	ExtBuilder::default().build().execute_with(|| {
		let stake = u32::max_value() as u64 * 2;
		let reward_slash = u32::max_value() as u64 * 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);
		<Stakers<Test>>::insert(&11, Exposure { total: stake, own: stake, others: vec![] });

		// Check reward
		let _ = Staking::reward_validator(&11, reward_slash);
		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();
		<Stakers<Test>>::insert(&11, Exposure { total: stake, own: 1, others: vec![
			IndividualExposure { who: 2, value: stake - 1 }
		]});


		// Check slashing
		on_offence_now(
			&[
				OffenceDetails {
					offender: (11, Staking::stakers(&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().execute_with(|| {
		use pallet_authorship::EventHandler;

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

		<Module<Test>>::note_author(11);
		<Module<Test>>::note_uncle(21, 1);
		// An uncle author that is not currently elected doesn't get rewards,
		// but the block producer does get reward for referencing it.
		<Module<Test>>::note_uncle(31, 1);
		// Rewarding the same two times works.
		<Module<Test>>::note_uncle(11, 1);

		// Not mandatory but must be coherent with rewards
		assert_eq!(<CurrentElected<Test>>::get(), vec![21, 11]);

		// 21 is rewarded as an uncle producer
		// 11 is rewarded as a block producer and uncle referencer and uncle producer
		assert_eq!(CurrentEraPointsEarned::get().individual, vec![1, 20 + 2 * 3 + 1]);
		assert_eq!(CurrentEraPointsEarned::get().total, 28);
	})
}

#[test]
fn add_reward_points_fns_works() {
	ExtBuilder::default().build().execute_with(|| {
		let validators = <Module<Test>>::current_elected();
		// Not mandatory but must be coherent with rewards
		assert_eq!(validators, vec![21, 11]);

		<Module<Test>>::reward_by_indices(vec![
			(0, 1),
			(1, 1),
			(2, 1),
			(1, 1),
		]);

		<Module<Test>>::reward_by_ids(vec![
			(21, 1),
			(11, 1),
			(31, 1),
			(11, 1),
		]);

		assert_eq!(CurrentEraPointsEarned::get().individual, vec![2, 4]);
		assert_eq!(CurrentEraPointsEarned::get().total, 6);
	})
}

#[test]
fn unbonded_balance_is_not_slashable() {
	ExtBuilder::default().build().execute_with(|| {
		// 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().execute_with(|| {
		start_era(1);
		assert_eq!(Staking::current_era_start_session_index(), SessionsPerEra::get());

		start_era(2);
		assert_eq!(Staking::current_era_start_session_index(), SessionsPerEra::get() * 2);

		let session = Session::current_index();
		ForceEra::put(Forcing::ForceNew);
		advance_session();
		assert_eq!(Staking::current_era(), 3);
		assert_eq!(Staking::current_era_start_session_index(), session + 1);

		start_era(4);
		assert_eq!(Staking::current_era_start_session_index(), session + SessionsPerEra::get() + 1);
	});
}

#[test]
fn offence_forces_new_era() {
	ExtBuilder::default().build().execute_with(|| {
		on_offence_now(
			&[OffenceDetails {
				offender: (
					11,
					Staking::stakers(&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().execute_with(|| {
		assert_ok!(Staking::force_new_era_always(Origin::ROOT));

		on_offence_now(
			&[OffenceDetails {
				offender: (
					11,
					Staking::stakers(&11),
				),
				reporters: vec![],
			}],
			&[Perbill::from_percent(5)],
		);

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

#[test]
fn offence_deselects_validator_when_slash_is_zero() {
	ExtBuilder::default().build().execute_with(|| {
		assert!(<Validators<Test>>::exists(11));
		on_offence_now(
			&[OffenceDetails {
				offender: (
					11,
					Staking::stakers(&11),
				),
				reporters: vec![],
			}],
			&[Perbill::from_percent(0)],
		);
		assert_eq!(Staking::force_era(), Forcing::ForceNew);
		assert!(!<Validators<Test>>::exists(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().execute_with(|| {
		assert_eq!(Staking::stakers(&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().execute_with(|| {
		start_era(1);

		assert!(<Validators<Test>>::exists(11));
		on_offence_now(
			&[OffenceDetails {
				offender: (
					11,
					Staking::stakers(&11),
				),
				reporters: vec![],
			}],
			&[Perbill::from_percent(0)],
		);
		assert_eq!(Staking::force_era(), Forcing::ForceNew);
		assert!(!<Validators<Test>>::exists(11));

		start_era(2);

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

		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::stakers(&11),
				),
				reporters: vec![],
			}],
			&[Perbill::from_percent(0)],
			1,
		);

		// not for zero-slash.
		assert_eq!(Staking::force_era(), Forcing::NotForcing);
		assert!(<Validators<Test>>::exists(11));

		on_offence_in_era(
			&[OffenceDetails {
				offender: (
					11,
					Staking::stakers(&11),
				),
				reporters: vec![],
			}],
			&[Perbill::from_percent(100)],
			1,
		);

		// or non-zero.
		assert_eq!(Staking::force_era(), Forcing::NotForcing);
		assert!(<Validators<Test>>::exists(11));
		assert_ledger_consistent(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().execute_with(|| {
		// The reporters' reward is calculated from the total exposure.
		let initial_balance = 1125;

		assert_eq!(Staking::stakers(&11).total, initial_balance);

		on_offence_now(
			&[OffenceDetails {
				offender: (
					11,
					Staking::stakers(&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);
		assert_ledger_consistent(11);
	});
}

#[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.
	ExtBuilder::default().build().execute_with(|| {
		// The reporters' reward is calculated from the total exposure.
		let initial_balance = 1125;

		assert_eq!(Staking::stakers(&11).total, initial_balance);

		on_offence_now(
			&[OffenceDetails {
				offender: (
					11,
					Staking::stakers(&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::stakers(&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);
		assert_ledger_consistent(11);
	});
}

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

		let exposure = Staking::stakers(&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::stakers(&11)),
					reporters: vec![],
				},
				OffenceDetails {
					offender: (21, Staking::stakers(&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),
			);
		}
		assert_ledger_consistent(11);
		assert_ledger_consistent(21);
	});
}

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

		on_offence_now(
			&[OffenceDetails {
				offender: (
					11,
					Staking::stakers(&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_ledger_consistent(11);
	});
}

#[test]
fn only_slash_for_max_in_era() {
	ExtBuilder::default().build().execute_with(|| {
		assert_eq!(Balances::free_balance(11), 1000);

		on_offence_now(
			&[
				OffenceDetails {
					offender: (11, Staking::stakers(&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::stakers(&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::stakers(&11)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(60)],
		);

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

#[test]
fn garbage_collection_after_slashing() {
	ExtBuilder::default().existential_deposit(1).build().execute_with(|| {
		assert_eq!(Balances::free_balance(11), 256_000);

		on_offence_now(
			&[
				OffenceDetails {
					offender: (11, Staking::stakers(&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::stakers(&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!(<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() {
	ExtBuilder::default().build().execute_with(|| {
		start_era(1);

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

		let exposure = Staking::stakers(&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::stakers(&11)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(10)],
		);

		let now = Staking::current_era();

		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());

			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().execute_with(|| {
		start_era(1);
		start_era(2);
		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::stakers(&11);
		let exposure_21 = Staking::stakers(&21);
		assert_eq!(Balances::free_balance(101), 2000);
		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::stakers(&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::stakers(&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::stakers(&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().execute_with(|| {
		start_era(1);
		start_era(2);
		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::stakers(&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();

		start_era(4);

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

		on_offence_now(
			&[
				OffenceDetails {
					offender: (21, Staking::stakers(&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().execute_with(|| {
		start_era(1);

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

		let exposure = Staking::stakers(&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::stakers(&11)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(10)],
		);

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

		start_era(2);

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

		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.
		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().execute_with(|| {
		start_era(1);

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

		let exposure = Staking::stakers(&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);

		start_era(2);

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

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

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

		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.
		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);

		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().execute_with(|| {
		start_era(1);

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

		let exposure = Staking::stakers(&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::stakers(&21)),
					reporters: vec![],
				}
			],
			&[Perbill::from_percent(10)],
		);

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

		assert_eq!(<Staking as Store>::UnappliedSlashes::get(&1).len(), 3);
		Staking::cancel_deferred_slash(Origin::ROOT, 1, vec![0, 2]).unwrap();

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

#[test]
fn version_initialized() {
	ExtBuilder::default().build().execute_with(|| {
		assert_eq!(<Staking as Store>::StorageVersion::get(), crate::migration::CURRENT_VERSION);
	});
}

#[test]
fn slash_kicks_validators_not_nominators() {
	ExtBuilder::default().build().execute_with(|| {
		start_era(1);

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

		let exposure = Staking::stakers(&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), 900);
		assert_eq!(Balances::free_balance(101), 2000 - (nominated_value / 10));

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

#[test]
fn migration_v2() {
	ExtBuilder::default().build().execute_with(|| {
		use crate::{EraIndex, slashing::SpanIndex};

		#[derive(Encode)]
		struct V1SlashingSpans {
			span_index: SpanIndex,
			last_start: EraIndex,
			prior: Vec<EraIndex>,
		}

		// inject old-style values directly into storage.
		let set = |stash, spans: V1SlashingSpans| {
			let key = <Staking as Store>::SlashingSpans::hashed_key_for(stash);
			sp_io::storage::set(&key, &spans.encode());
		};

		let spans_11 = V1SlashingSpans {
			span_index: 10,
			last_start: 1,
			prior: vec![0],
		};

		let spans_21 = V1SlashingSpans {
			span_index: 1,
			last_start: 5,
			prior: vec![],
		};

		set(11, spans_11);
		set(21, spans_21);

		<Staking as Store>::StorageVersion::put(1);

		// perform migration.
		crate::migration::inner::to_v2::<Test>(&mut 1);

		assert_eq!(
			<Staking as Store>::SlashingSpans::get(&11).unwrap().last_nonzero_slash(),
			1,
		);

		assert_eq!(
			<Staking as Store>::SlashingSpans::get(&21).unwrap().last_nonzero_slash(),
			5,
		);
	});
}

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

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

		let exposure = Staking::stakers(&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::enumerate() {
			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);
	});
}