// Copyright 2017-2019 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.

#![cfg(test)]

use super::*;
use runtime_io::with_externalities;
use phragmen;
use srml_support::{assert_ok, assert_noop, assert_eq_uvec, EnumerableStorageMap};
use mock::{Balances, Session, Staking, System, Timestamp, Test, ExtBuilder, Origin};
use srml_support::traits::{Currency, ReservableCurrency};

#[inline]
fn check_exposure(acc: u64) {
	let expo = Staking::stakers(&acc);
	assert_eq!(expo.total as u128, expo.own as u128 + expo.others.iter().map(|e| e.value as u128).sum::<u128>());
}

#[inline]
fn check_exposure_all() {
	Staking::current_elected().into_iter().for_each(|acc| check_exposure(acc));
}

#[inline]
fn assert_total_expo(acc: u64, val: u64) {
	let expo = Staking::stakers(&acc);
	assert_eq!(expo.total, val);
}

#[inline]
fn bond_validator(acc: u64, val: u64) {
	// a = controller
	// a + 1 = stash
	let _ = Balances::make_free_balance_be(&(acc+1), val);
	assert_ok!(Staking::bond(Origin::signed(acc+1), acc, val, RewardDestination::Controller));
	assert_ok!(Staking::validate(Origin::signed(acc), ValidatorPrefs::default()));
}

#[inline]
fn bond_nominator(acc: u64, val: u64, target: Vec<u64>) {
	// a = controller
	// a + 1 = stash
	let _ = Balances::make_free_balance_be(&(acc+1), val);
	assert_ok!(Staking::bond(Origin::signed(acc+1), acc, val, RewardDestination::Controller));
	assert_ok!(Staking::nominate(Origin::signed(acc), target));
}

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

		// 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, thus unstake_threshold is 3, other values are default for their type
		assert_eq!(<Validators<Test>>::enumerate().collect::<Vec<_>>(), vec![
			(31, ValidatorPrefs { unstake_threshold: 3, validator_payment: 0 }),
			(21, ValidatorPrefs { unstake_threshold: 3, validator_payment: 0 }),
			(11, ValidatorPrefs { unstake_threshold: 3, validator_payment: 0 })
		]);

		// Account 100 is the default nominator
		assert_eq!(Staking::ledger(100), Some(StakingLedger { stash: 101, total: 500, active: 500, unlocking: vec![] }));
		assert_eq!(Staking::nominators(101), vec![11, 21]);

		// Account 10 is exposed by 1000 * balance_factor from their own stash in account 11 + the default nominator vote
		assert_eq!(Staking::stakers(11), Exposure { total: 1125, own: 1000, others: vec![ IndividualExposure { who: 101, value: 125 }] });
		// Account 20 is exposed by 1000 * balance_factor from their own stash in account 21 + the default nominator vote
		assert_eq!(Staking::stakers(21), Exposure { total: 1375, own: 1000, others: vec![ IndividualExposure { who: 101, value: 375 }] });

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

		// Initial Era and session
		assert_eq!(Staking::current_era(), 0);
		assert_eq!(Session::current_index(), 0);

		// initial rewards
		assert_eq!(Staking::current_session_reward(), 10);

		// initial slot_stake
		assert_eq!(Staking::slot_stake(),  1125); // Naive

		// initial slash_count of validators
		assert_eq!(Staking::slash_count(&11), 0);
		assert_eq!(Staking::slash_count(&21), 0);

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

#[test]
fn no_offline_should_work() {
	// Test the staking module works when no validators are offline
	with_externalities(&mut ExtBuilder::default().build(),
	|| {
		// Slashing begins for validators immediately if found offline
		assert_eq!(Staking::offline_slash_grace(), 0);
		// Account 10 has not been reported offline
		assert_eq!(Staking::slash_count(&10), 0);
		// Account 10 has `balance_factor` free balance
		assert_eq!(Balances::free_balance(&10), 1);
		// Nothing happens to Account 10, as expected
		assert_eq!(Staking::slash_count(&10), 0);
		assert_eq!(Balances::free_balance(&10), 1);
		// New era is not being forced
		assert!(Staking::forcing_new_era().is_none());
	});
}

#[test]
fn change_controller_works() {
	with_externalities(&mut ExtBuilder::default().build(),
	|| {
		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));

		System::set_block_number(1);
		Session::check_rotate_session(System::block_number());
		assert_eq!(Staking::current_era(), 1);

		assert_noop!(
			Staking::validate(Origin::signed(10), ValidatorPrefs::default()),
			"not a controller"
		);
		assert_ok!(Staking::validate(Origin::signed(5), ValidatorPrefs::default()));
	})
}

#[test]
fn invulnerability_should_work() {
	// Test that users can be invulnerable from slashing and being kicked
	with_externalities(&mut ExtBuilder::default().build(),
	|| {
		// Make account 11 invulnerable
		assert_ok!(Staking::set_invulnerables(vec![11]));
		// Give account 11 some funds
		let _ = Balances::make_free_balance_be(&11, 70);
		// There is no slash grace -- slash immediately.
		assert_eq!(Staking::offline_slash_grace(), 0);
		// Account 11 has not been slashed
		assert_eq!(Staking::slash_count(&11), 0);
		// Account 11 has the 70 funds we gave it above
		assert_eq!(Balances::free_balance(&11), 70);
		// Account 11 should be a validator
		assert!(<Validators<Test>>::exists(&11));

		// Set account 11 as an offline validator with a large number of reports
		// Should exit early if invulnerable
		Staking::on_offline_validator(10, 100);

		// Show that account 11 has not been touched
		assert_eq!(Staking::slash_count(&11), 0);
		assert_eq!(Balances::free_balance(&11), 70);
		assert!(<Validators<Test>>::exists(&11));
		// New era not being forced
		// NOTE: new era is always forced once slashing happens -> new validators need to be chosen.
		assert!(Staking::forcing_new_era().is_none());
	});
}

#[test]
fn offline_should_slash_and_kick() {
	// Test that an offline validator gets slashed and kicked
	with_externalities(&mut ExtBuilder::default().build(), || {
		// Give account 10 some balance
		let _ = Balances::make_free_balance_be(&11, 1000);
		// Confirm account 10 is a validator
		assert!(<Validators<Test>>::exists(&11));
		// Validators get slashed immediately
		assert_eq!(Staking::offline_slash_grace(), 0);
		// Unstake threshold is 3
		assert_eq!(Staking::validators(&11).unstake_threshold, 3);
		// Account 10 has not been slashed before
		assert_eq!(Staking::slash_count(&11), 0);
		// Account 10 has the funds we just gave it
		assert_eq!(Balances::free_balance(&11), 1000);
		// Report account 10 as offline, one greater than unstake threshold
		Staking::on_offline_validator(10, 4);
		// Confirm user has been reported
		assert_eq!(Staking::slash_count(&11), 4);
		// Confirm balance has been reduced by 2^unstake_threshold * offline_slash() * amount_at_stake.
		let slash_base = Staking::offline_slash() * Staking::stakers(11).total;
		assert_eq!(Balances::free_balance(&11), 1000 - 2_u64.pow(3) * slash_base);
		// Confirm account 10 has been removed as a validator
		assert!(!<Validators<Test>>::exists(&11));
		// A new era is forced due to slashing
		assert!(Staking::forcing_new_era().is_some());
	});
}

#[test]
fn offline_grace_should_delay_slashing() {
	// Tests that with grace, slashing is delayed
	with_externalities(&mut ExtBuilder::default().build(), || {
		// Initialize account 10 with balance
		let _ = Balances::make_free_balance_be(&11, 70);
		// Verify account 11 has balance
		assert_eq!(Balances::free_balance(&11), 70);

		// Set offline slash grace
		let offline_slash_grace = 1;
		assert_ok!(Staking::set_offline_slash_grace(offline_slash_grace));
		assert_eq!(Staking::offline_slash_grace(), 1);

		// Check unstake_threshold is 3 (default)
		let default_unstake_threshold = 3;
		assert_eq!(Staking::validators(&11), ValidatorPrefs { unstake_threshold: default_unstake_threshold, validator_payment: 0 });

		// Check slash count is zero
		assert_eq!(Staking::slash_count(&11), 0);

		// Report account 10 up to the threshold
		Staking::on_offline_validator(10, default_unstake_threshold as usize + offline_slash_grace as usize);
		// Confirm slash count
		assert_eq!(Staking::slash_count(&11), 4);

		// Nothing should happen
		assert_eq!(Balances::free_balance(&11), 70);

		// Report account 10 one more time
		Staking::on_offline_validator(10, 1);
		assert_eq!(Staking::slash_count(&11), 5);
		// User gets slashed
		assert!(Balances::free_balance(&11) < 70);
		// New era is forced
		assert!(Staking::forcing_new_era().is_some());
	});
}


#[test]
fn max_unstake_threshold_works() {
	// Tests that max_unstake_threshold gets used when prefs.unstake_threshold is large
	with_externalities(&mut ExtBuilder::default().build(), || {
		const MAX_UNSTAKE_THRESHOLD: u32 = 10;
		// Two users with maximum possible balance
		let _ = Balances::make_free_balance_be(&11, u64::max_value());
		let _ = Balances::make_free_balance_be(&21, u64::max_value());

		// Give them full exposure as a staker
		<Stakers<Test>>::insert(&11, Exposure { total: 1000000, own: 1000000, others: vec![]});
		<Stakers<Test>>::insert(&21, Exposure { total: 2000000, own: 2000000, others: vec![]});

		// Check things are initialized correctly
		assert_eq!(Balances::free_balance(&11), u64::max_value());
		assert_eq!(Balances::free_balance(&21), u64::max_value());
		assert_eq!(Staking::offline_slash_grace(), 0);
		// Account 10 will have max unstake_threshold
		assert_ok!(Staking::validate(Origin::signed(10), ValidatorPrefs {
			unstake_threshold: MAX_UNSTAKE_THRESHOLD,
			validator_payment: 0,
		}));
		// Account 20 could not set their unstake_threshold past 10
		assert_noop!(Staking::validate(Origin::signed(20), ValidatorPrefs {
			unstake_threshold: MAX_UNSTAKE_THRESHOLD + 1,
			validator_payment: 0}),
			"unstake threshold too large"
		);
		// Give Account 20 unstake_threshold 11 anyway, should still be limited to 10
		<Validators<Test>>::insert(21, ValidatorPrefs {
			unstake_threshold: MAX_UNSTAKE_THRESHOLD + 1,
			validator_payment: 0,
		});

		<OfflineSlash<Test>>::put(Perbill::from_fraction(0.0001));

		// Report each user 1 more than the max_unstake_threshold
		Staking::on_offline_validator(10, MAX_UNSTAKE_THRESHOLD as usize + 1);
		Staking::on_offline_validator(20, MAX_UNSTAKE_THRESHOLD as usize + 1);

		// Show that each balance only gets reduced by 2^max_unstake_threshold times 10%
		// of their total stake.
		assert_eq!(Balances::free_balance(&11), u64::max_value() - 2_u64.pow(MAX_UNSTAKE_THRESHOLD) * 100);
		assert_eq!(Balances::free_balance(&21), u64::max_value() - 2_u64.pow(MAX_UNSTAKE_THRESHOLD) * 200);
	});
}

#[test]
fn slashing_does_not_cause_underflow() {
	// Tests that slashing more than a user has does not underflow
	with_externalities(&mut ExtBuilder::default().build(), || {
		// Verify initial conditions
		assert_eq!(Balances::free_balance(&11), 1000);
		assert_eq!(Staking::offline_slash_grace(), 0);

		// Set validator preference so that 2^unstake_threshold would cause overflow (greater than 64)
		<Validators<Test>>::insert(11, ValidatorPrefs {
			unstake_threshold: 10,
			validator_payment: 0,
		});

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

		// Should not panic
		Staking::on_offline_validator(10, 100);
		// Confirm that underflow has not occurred, and account balance is set to zero
		assert_eq!(Balances::free_balance(&11), 0);
	});
}


#[test]
fn rewards_should_work() {
	// should check that:
	// * rewards get recorded per session
	// * rewards get paid per Era
	// * Check that nominators are also rewarded
	with_externalities(&mut ExtBuilder::default()
		.session_length(3)
		.sessions_per_era(3)
	.build(),
	|| {
		let delay = 1;
		// this test is only in the scope of one era. Since this variable changes
		// at the last block/new era, we'll save it.
		let session_reward = 10;

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

		// Initial config should be correct
		assert_eq!(Staking::era_length(), 9);
		assert_eq!(Staking::sessions_per_era(), 3);
		assert_eq!(Staking::last_era_length_change(), 0);
		assert_eq!(Staking::current_era(), 0);
		assert_eq!(Session::current_index(), 0);
		assert_eq!(Staking::current_session_reward(), 10);

		// check the balance of a validator accounts.
		assert_eq!(Balances::total_balance(&11), 1000);
		// and the nominator (to-be)
		let _ = Balances::make_free_balance_be(&2, 500);
		assert_eq!(Balances::total_balance(&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);
		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*5);	// on time.
		Session::check_rotate_session(System::block_number());
		assert_eq!(Staking::current_era(), 0);
		assert_eq!(Session::current_index(), 1);

		// session triggered: the reward value stashed should be 10 -- defined in ExtBuilder genesis.
		assert_eq!(Staking::current_session_reward(), session_reward);
		assert_eq!(Staking::current_era_reward(), session_reward);

		block = 6; // Block 6 => Session 2 => Era 0
		System::set_block_number(block);
		Timestamp::set_timestamp(block*5 + delay);	// a little late.
		Session::check_rotate_session(System::block_number());
		assert_eq!(Staking::current_era(), 0);
		assert_eq!(Session::current_index(), 2);

		// session reward is the same,
		assert_eq!(Staking::current_session_reward(), session_reward);
		// though 2 will be deducted while stashed in the era reward due to delay
		assert_eq!(Staking::current_era_reward(), 2*session_reward - delay);

		block = 9; // Block 9 => Session 3 => Era 1
		System::set_block_number(block);
		Timestamp::set_timestamp(block*5);  // back to being on time. no delays
		Session::check_rotate_session(System::block_number());
		assert_eq!(Staking::current_era(), 1);
		assert_eq!(Session::current_index(), 3);

		assert_eq!(Balances::total_balance(&10), 1 + (3*session_reward - delay)/2);
		assert_eq!(Balances::total_balance(&2), 500 + (3*session_reward - delay)/2);
	});
}

#[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.
	with_externalities(&mut ExtBuilder::default()
		.session_length(3)
		.sessions_per_era(3)
		.nominate(false)
		.build(),
	|| {
		let delay = 1;
		let session_reward = 10;

		// This is set by the test config builder.
		assert_eq!(Staking::current_session_reward(), session_reward);

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

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

		let mut block = 3;
		// Block 3 => Session 1 => Era 0
		System::set_block_number(block);
		Timestamp::set_timestamp(block*5);
		Session::check_rotate_session(System::block_number());
		assert_eq!(Staking::current_era(), 0);
		assert_eq!(Session::current_index(), 1);

		// session triggered: the reward value stashed should be 10
		assert_eq!(Staking::current_session_reward(), session_reward);
		assert_eq!(Staking::current_era_reward(), session_reward);

		block = 6; // Block 6 => Session 2 => Era 0
		System::set_block_number(block);
		Timestamp::set_timestamp(block*5 + delay);	// a little late.
		Session::check_rotate_session(System::block_number());
		assert_eq!(Staking::current_era(), 0);
		assert_eq!(Session::current_index(), 2);

		assert_eq!(Staking::current_session_reward(), session_reward);
		assert_eq!(Staking::current_era_reward(), 2*session_reward - delay);

		block = 9; // Block 9 => Session 3 => Era 1
		System::set_block_number(block);
		Timestamp::set_timestamp(block*5);  // back to being punktlisch. no delayss
		Session::check_rotate_session(System::block_number());
		assert_eq!(Staking::current_era(), 1);
		assert_eq!(Session::current_index(), 3);

		// 1 + sum of of the session rewards accumulated
		let recorded_balance = 1 + 3*session_reward - delay;
		assert_eq!(Balances::total_balance(&10), recorded_balance);

		// the reward for next era will be: session_reward * slot_stake
		let new_session_reward = Staking::session_reward() * Staking::slot_stake();
		assert_eq!(Staking::current_session_reward(), new_session_reward);

		// fast forward to next era:
		block=12; System::set_block_number(block);Timestamp::set_timestamp(block*5);Session::check_rotate_session(System::block_number());
		block=15; System::set_block_number(block);Timestamp::set_timestamp(block*5);Session::check_rotate_session(System::block_number());

		// intermediate test.
		assert_eq!(Staking::current_era_reward(), 2*new_session_reward);

		// new era is triggered here.
		block=18; System::set_block_number(block);Timestamp::set_timestamp(block*5);Session::check_rotate_session(System::block_number());

		// pay time
		assert_eq!(Balances::total_balance(&10), 3*new_session_reward + recorded_balance);
	});
}

#[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.
	with_externalities(&mut ExtBuilder::default()
		.sessions_per_era(3)
		.nominate(false)
		.fair(false) // to give 20 more staked value
		.build(),
	|| {
		// remember + compare this along with the test.
		assert_eq_uvec!(Session::validators(), vec![20, 10]);

		assert_ok!(Staking::set_bonding_duration(2));
		assert_eq!(Staking::bonding_duration(), 2);

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

		// --- Block 1:
		System::set_block_number(1);
		Session::check_rotate_session(System::block_number());
		assert_eq!(Staking::current_era(), 0);

		// 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!(Session::validators(), vec![20, 10]);

		// --- Block 2:
		System::set_block_number(2);
		Session::check_rotate_session(System::block_number());
		assert_eq!(Staking::current_era(), 0);

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


		// --- Block 3: the validators will now change.
		System::set_block_number(3);
		Session::check_rotate_session(System::block_number());

		// 2 only voted for 4 and 20
		assert_eq!(Session::validators().len(), 2);
		assert_eq_uvec!(Session::validators(), vec![20, 4]);
		assert_eq!(Staking::current_era(), 1);


		// --- Block 4: Unstake 4 as a validator, freeing up the balance stashed in 3
		System::set_block_number(4);
		Session::check_rotate_session(System::block_number());

		// 4 will chill
		Staking::chill(Origin::signed(4)).unwrap();

		// nothing should be changed so far.
		assert_eq_uvec!(Session::validators(), vec![20, 4]);
		assert_eq!(Staking::current_era(), 1);


		// --- Block 5: nothing. 4 is still there.
		System::set_block_number(5);
		Session::check_rotate_session(System::block_number());
		assert_eq_uvec!(Session::validators(), vec![20, 4]);
		assert_eq!(Staking::current_era(), 1);


		// --- Block 6: 4 will not be a validator.
		System::set_block_number(6);
		Session::check_rotate_session(System::block_number());
		assert_eq!(Staking::current_era(), 2);
		assert_eq!(Session::validators().contains(&4), false);
		assert_eq_uvec!(Session::validators(), 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), "account liquidity restrictions prevent withdrawal");
		assert_ok!(Balances::reserve(&3, 409));
	});
}

#[test]
fn less_than_needed_candidates_works() {
	with_externalities(&mut ExtBuilder::default()
		.minimum_validator_count(1)
		.validator_count(4)
		.nominate(false)
		.build(),
	|| {
		assert_eq!(Staking::validator_count(), 4);
		assert_eq!(Staking::minimum_validator_count(), 1);
		assert_eq_uvec!(Session::validators(), vec![30, 20, 10]);

		System::set_block_number(1);
		Session::check_rotate_session(System::block_number());
		assert_eq!(Staking::current_era(), 1);

		// Previous set is selected. NO election algorithm is even executed.
		assert_eq_uvec!(Session::validators(), 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();
	});
}

#[test]
fn no_candidate_emergency_condition() {
	// Test the situation where the number of validators are less than `ValidatorCount` and less than <MinValidators>
	// The expected behavior is to choose all candidates from the previous era.
	with_externalities(&mut ExtBuilder::default()
		.minimum_validator_count(10)
		.validator_count(15)
		.validator_pool(true)
		.nominate(false)
		.build(),
	|| {
		assert_eq!(Staking::era_length(), 1);
		assert_eq!(Staking::validator_count(), 15);

		// initial validators
		assert_eq_uvec!(Session::validators(), vec![10, 20, 30, 40]);

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

		// trigger era
		System::set_block_number(1);
		Session::check_rotate_session(System::block_number());

		// Previous ones are elected. chill is invalidates. TODO: #2494
		assert_eq_uvec!(Session::validators(), vec![10, 20, 30, 40]);
		assert_eq!(Staking::current_elected().len(), 0);
	});
}

#[test]
fn nominating_and_rewards_should_work() {
	// PHRAGMEN OUTPUT: running this test with the reference impl gives:
	//
	// Votes  [('10', 1000, ['10']), ('20', 1000, ['20']), ('30', 1000, ['30']), ('40', 1000, ['40']), ('2', 1000, ['10', '20', '30']), ('4', 1000, ['10', '20', '40'])]
	// 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

	with_externalities(&mut ExtBuilder::default()
		.nominate(false)
		.validator_pool(true)
		.build(),
	|| {
		// initial validators -- everyone is actually even.
		assert_eq_uvec!(Session::validators(), 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));

		// default reward for the first session.
		let session_reward = 10;
		assert_eq!(Staking::current_session_reward(), session_reward);

		// 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]));

		System::set_block_number(1);
		Session::check_rotate_session(System::block_number());
		assert_eq!(Staking::current_era(), 1);

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

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

		// ------ 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<BalanceOf<Test>>>(), 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!(Staking::stakers(21).total, 1000 + 1198);
		// 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![599, 599]);
		assert_eq!(Staking::stakers(21).others.iter().map(|e| e.who).collect::<Vec<BalanceOf<Test>>>(), vec![3, 1]);

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


		System::set_block_number(2);
		Session::check_rotate_session(System::block_number());
		// next session reward.
		let new_session_reward = Staking::session_reward() * Staking::slot_stake();
		// nothing else will happen, era ends and rewards are paid again,
		// it is expected that nominators will also be paid. See below

		// Nominator 2: has [400/1800 ~ 2/9 from 10] + [600/2200 ~ 3/11 from 20]'s reward. ==> 2/9 + 3/11
		assert_eq!(Balances::total_balance(&2), initial_balance + (2*new_session_reward/9 + 3*new_session_reward/11));
		// Nominator 4: has [400/1800 ~ 2/9 from 10] + [600/2200 ~ 3/11 from 20]'s reward. ==> 2/9 + 3/11
		assert_eq!(Balances::total_balance(&4), initial_balance + (2*new_session_reward/9 + 3*new_session_reward/11));

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

		check_exposure_all();
	});
}

#[test]
fn nominators_also_get_slashed() {
	// A nominator should be slashed if the validator they nominated is slashed
	with_externalities(&mut ExtBuilder::default().nominate(false).build(), || {
		assert_eq!(Staking::era_length(), 1);
		assert_eq!(Staking::validator_count(), 2);
		// slash happens immediately.
		assert_eq!(Staking::offline_slash_grace(), 0);
		// Account 10 has not been reported offline
		assert_eq!(Staking::slash_count(&10), 0);
		<OfflineSlash<Test>>::put(Perbill::from_percent(12));

		// 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
		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]));

		// new era, pay rewards,
		System::set_block_number(1);
		Session::check_rotate_session(System::block_number());

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

		// 10 goes offline
		Staking::on_offline_validator(10, 4);
		let expo = Staking::stakers(10);
		let slash_value = Staking::offline_slash() * expo.total * 2_u64.pow(3);
		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(&10), initial_balance + 10 - validator_slash);
		assert_eq!(Balances::total_balance(&2), initial_balance - nominator_slash);
		check_exposure_all();
		// Because slashing happened.
		assert!(Staking::forcing_new_era().is_some());
	});
}

#[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.
	with_externalities(&mut ExtBuilder::default()
		.sessions_per_era(2)
		.build(),
		|| {
			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()), "stash already bonded");
			// 1 = stashed => attempting to nominate should fail.
			assert_noop!(Staking::nominate(Origin::signed(1), vec![1]), "not a controller");
			// 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.
	with_externalities(&mut ExtBuilder::default()
		.sessions_per_era(2)
		.build(),
		|| {
			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()), "controller already paired");
		});
}

#[test]
fn session_and_eras_work() {
	with_externalities(&mut ExtBuilder::default()
		.sessions_per_era(2)
		.build(),
	|| {
		assert_eq!(Staking::era_length(), 2);
		assert_eq!(Staking::sessions_per_era(), 2);
		assert_eq!(Staking::last_era_length_change(), 0);
		assert_eq!(Staking::current_era(), 0);
		assert_eq!(Session::current_index(), 0);

		// Block 1: No change.
		System::set_block_number(1);
		Session::check_rotate_session(System::block_number());
		assert_eq!(Session::current_index(), 1);
		assert_eq!(Staking::sessions_per_era(), 2);
		assert_eq!(Staking::last_era_length_change(), 0);
		assert_eq!(Staking::current_era(), 0);

		// Block 2: Simple era change.
		System::set_block_number(2);
		Session::check_rotate_session(System::block_number());
		assert_eq!(Session::current_index(), 2);
		assert_eq!(Staking::sessions_per_era(), 2);
		assert_eq!(Staking::last_era_length_change(), 0);
		assert_eq!(Staking::current_era(), 1);

		// Block 3: Schedule an era length change; no visible changes.
		System::set_block_number(3);
		assert_ok!(Staking::set_sessions_per_era(3));
		Session::check_rotate_session(System::block_number());
		assert_eq!(Session::current_index(), 3);
		assert_eq!(Staking::sessions_per_era(), 2);
		assert_eq!(Staking::last_era_length_change(), 0);
		assert_eq!(Staking::current_era(), 1);

		// Block 4: Era change kicks in.
		System::set_block_number(4);
		Session::check_rotate_session(System::block_number());
		assert_eq!(Session::current_index(), 4);
		assert_eq!(Staking::sessions_per_era(), 3);
		assert_eq!(Staking::last_era_length_change(), 4);
		assert_eq!(Staking::current_era(), 2);

		// Block 5: No change.
		System::set_block_number(5);
		Session::check_rotate_session(System::block_number());
		assert_eq!(Session::current_index(), 5);
		assert_eq!(Staking::sessions_per_era(), 3);
		assert_eq!(Staking::last_era_length_change(), 4);
		assert_eq!(Staking::current_era(), 2);

		// Block 6: No change.
		System::set_block_number(6);
		Session::check_rotate_session(System::block_number());
		assert_eq!(Session::current_index(), 6);
		assert_eq!(Staking::sessions_per_era(), 3);
		assert_eq!(Staking::last_era_length_change(), 4);
		assert_eq!(Staking::current_era(), 2);

		// Block 7: Era increment.
		System::set_block_number(7);
		Session::check_rotate_session(System::block_number());
		assert_eq!(Session::current_index(), 7);
		assert_eq!(Staking::sessions_per_era(), 3);
		assert_eq!(Staking::last_era_length_change(), 4);
		assert_eq!(Staking::current_era(), 3);
	});
}

#[test]
fn cannot_transfer_staked_balance() {
	// Tests that a stash account cannot transfer funds
	with_externalities(&mut ExtBuilder::default().nominate(false).build(), || {
		// 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), "account liquidity restrictions prevent withdrawal");

		// 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
	with_externalities(&mut ExtBuilder::default()
		.nominate(false)
		.fair(true)
		.build(),
	|| {
		// 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), "account liquidity restrictions prevent withdrawal");
		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
	with_externalities(&mut ExtBuilder::default().build(), || {
		// 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), "account liquidity restrictions prevent withdrawal");

		// 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
	with_externalities(&mut ExtBuilder::default().nominate(false).build(), || {
		// 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![] }));
		// Check current session reward is 10
		let session_reward0 = Staking::current_session_reward(); // 10

		// Move forward the system for payment
		System::set_block_number(1);
		Timestamp::set_timestamp(5);
		Session::check_rotate_session(System::block_number());

		// 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 + session_reward0);
		// Check that amount at stake increased accordingly
		assert_eq!(Staking::ledger(&10), Some(StakingLedger { stash: 11, total: 1000 + session_reward0, active: 1000 + session_reward0, unlocking: vec![] }));
		// Update current session reward
		let session_reward1 = Staking::current_session_reward(); // 1010 (1* slot_stake)

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

		// Move forward the system for payment
		System::set_block_number(2);
		Timestamp::set_timestamp(10);
		Session::check_rotate_session(System::block_number());

		// 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 + session_reward0 + session_reward1);
		// Record this value
		let recorded_stash_balance = 1000 + session_reward0 + session_reward1;
		// Check that amount at stake is NOT increased
		assert_eq!(Staking::ledger(&10), Some(StakingLedger { stash: 11, total: 1000 + session_reward0, active: 1000 + session_reward0, unlocking: vec![] }));

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

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

		// Move forward the system for payment
		System::set_block_number(3);
		Timestamp::set_timestamp(15);
		Session::check_rotate_session(System::block_number());
		let session_reward2 = Staking::current_session_reward(); // 1010 (1* slot_stake)

		// 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 + session_reward2);
		// Check that amount at stake is NOT increased
		assert_eq!(Staking::ledger(&10), Some(StakingLedger { stash: 11, total: 1000 + session_reward0, active: 1000 + session_reward0, 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.
	with_externalities(&mut ExtBuilder::default()
		.session_length(3)
		.sessions_per_era(3)
		.build(),
	|| {
		// Initial config
		let session_reward = 10;
		let validator_cut = 5;
		let stash_initial_balance = Balances::total_balance(&11);
		assert_eq!(Staking::current_session_reward(), session_reward);

		// 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 {
			unstake_threshold: 3,
			validator_payment: validator_cut
		});

		// ------------ Fast forward
		// Block 3 => Session 1 => Era 0
		let mut block = 3;
		System::set_block_number(block);
		Session::check_rotate_session(System::block_number());
		assert_eq!(Staking::current_era(), 0);
		assert_eq!(Session::current_index(), 1);

		// session triggered: the reward value stashed should be 10 -- defined in ExtBuilder genesis.
		assert_eq!(Staking::current_session_reward(), session_reward);
		assert_eq!(Staking::current_era_reward(), session_reward);

		block = 6; // Block 6 => Session 2 => Era 0
		System::set_block_number(block);
		Session::check_rotate_session(System::block_number());
		assert_eq!(Staking::current_era(), 0);
		assert_eq!(Session::current_index(), 2);

		assert_eq!(Staking::current_session_reward(), session_reward);
		assert_eq!(Staking::current_era_reward(), 2*session_reward);

		block = 9; // Block 9 => Session 3 => Era 1
		System::set_block_number(block);
		Session::check_rotate_session(System::block_number());
		assert_eq!(Staking::current_era(), 1);
		assert_eq!(Session::current_index(), 3);

		// whats left to be shared is the sum of 3 rounds minus the validator's cut.
		let shared_cut = 3 * session_reward - validator_cut;
		// Validator's payee is Staked account, 11, reward will be paid here.
		assert_eq!(Balances::total_balance(&11), stash_initial_balance + shared_cut/2 + validator_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();
	});

}

#[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`.
	with_externalities(&mut ExtBuilder::default().build(),
	|| {
		// 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.
	with_externalities(&mut ExtBuilder::default()
		.nominate(false)
		.build(),
	|| {
		// Set payee to controller. avoids confusion
		assert_ok!(Staking::set_payee(Origin::signed(10), RewardDestination::Controller));

		// Set unbonding era (bonding_duration) to 2
		assert_ok!(Staking::set_bonding_duration(2));

		// 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::sessions_per_era(), 1);
		assert_eq!(Staking::current_era(), 0);
		assert_eq!(Session::current_index(), 0);
		assert_eq!(Staking::current_session_reward(), 10);

		// 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.
		System::set_block_number(1);
		Session::check_rotate_session(System::block_number());

		// 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.
		System::set_block_number(2);Timestamp::set_timestamp(10);Session::check_rotate_session(System::block_number());
		assert_eq!(Staking::current_era(), 2);
		assert_eq!(Session::current_index(), 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 + 2}] })
		);

		// 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 + 2}] }));

		// trigger next era.
		System::set_block_number(3);
		Session::check_rotate_session(System::block_number());

		assert_eq!(Staking::current_era(), 3);
		assert_eq!(Session::current_index(), 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 + 2}] }));

		// trigger next era.
		System::set_block_number(4);
		Session::check_rotate_session(System::block_number());
		assert_eq!(Staking::current_era(), 4);
		assert_eq!(Session::current_index(), 4);

		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 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
	with_externalities(&mut ExtBuilder::default()
		.nominate(false)
		.fair(false)
		.build(),
	|| {
		// 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![] });

		// New era --> rewards are paid --> stakes are changed
		System::set_block_number(1);
		Session::check_rotate_session(System::block_number());
		assert_eq!(Staking::current_era(), 1);

		// -- new balances + reward
		assert_eq!(Staking::stakers(&11).total, 1000 + 10);
		assert_eq!(Staking::stakers(&21).total, 69 + 10);

		// -- slot stake should also be updated.
		assert_eq!(Staking::slot_stake(), 79);

		// If 10 gets slashed now, it will be slashed by 5% of exposure.total * 2.pow(unstake_thresh)
		Staking::on_offline_validator(10, 4);
		// Confirm user has been reported
		assert_eq!(Staking::slash_count(&11), 4);
		// check the balance of 10 (slash will be deducted from free balance.)
		assert_eq!(Balances::free_balance(&11), 1000 + 10 - 50 /*5% of 1000*/ * 8 /*2**3*/);

		check_exposure_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
	with_externalities(&mut ExtBuilder::default()
		.existential_deposit(10)
		.build(),
	|| {
		// 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
		// Initiate slash count storage item
		Staking::on_offline_validator(10, 1);
		// 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!(<SlashCount<Test>>::exists(&11));
		assert!(<Payee<Test>>::exists(&11));

		// Reduce free_balance of controller to 0
		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!(<SlashCount<Test>>::exists(&11));
		assert!(<Payee<Test>>::exists(&11));

		// Reduce free_balance of stash to 0
		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!(!<SlashCount<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
	with_externalities(&mut ExtBuilder::default()
		.existential_deposit(10)
		.build(),
	|| {
		// 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
		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
		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!(!<SlashCount<Test>>::exists(&11));
		assert!(!<Payee<Test>>::exists(&11));
	});
}

#[test]
fn phragmen_poc_works() {
	// Tests the POC test of the phragmen, mentioned in the paper and reference implementation.
	// Initial votes:
	// Votes  [
	// ('2', 500, ['10', '20', '30']),
	// ('4', 500, ['10', '20', '40']),
	// ('10', 1000, ['10']),
	// ('20', 1000, ['20']),
	// ('30', 1000, ['30']),
	// ('40', 1000, ['40'])]
	//
	// Sequential Phragmén gives
	// 10  is elected with stake  1666.6666666666665 and score  0.0005
	// 20  is elected with stake  1333.3333333333333 and score  0.00075

	// 2  has load  0.00075 and supported
	// 10  with stake  333.3333333333333 20  with stake  166.66666666666666 30  with stake  0.0
	// 4  has load  0.00075 and supported
	// 10  with stake  333.3333333333333 20  with stake  166.66666666666666 40  with stake  0.0
	// 10  has load  0.0005 and supported
	// 10  with stake  1000.0
	// 20  has load  0.00075 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

	// 	Sequential Phragmén with post processing gives
	// 10  is elected with stake  1500.0 and score  0.0005
	// 20  is elected with stake  1500.0 and score  0.00075
	//
	// 10  has load  0.0005 and supported
	// 10  with stake  1000.0
	// 20  has load  0.00075 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  0.00075 and supported
	// 10  with stake  166.66666666666674 20  with stake  333.33333333333326 30  with stake  0
	// 4  has load  0.00075 and supported
	// 10  with stake  333.3333333333333 20  with stake  166.66666666666666 40  with stake  0.0


	with_externalities(&mut ExtBuilder::default()
		.nominate(false)
		.validator_pool(true)
		.build(),
	|| {
		// We don't really care about this. At this point everything is even.
		assert_eq_uvec!(Session::validators(), vec![40, 30]);

		// Set payees 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));

		// no one is a nominator
		assert_eq!(<Nominators<Test>>::enumerate().count(), 0 as usize);

		// bond [2,1] / [4,3] a nominator
		let _ = Balances::deposit_creating(&1, 1000);
		let _ = Balances::deposit_creating(&3, 1000);

		assert_ok!(Staking::bond(Origin::signed(1), 2, 500, RewardDestination::default()));
		assert_ok!(Staking::nominate(Origin::signed(2), vec![11, 21, 31]));

		assert_ok!(Staking::bond(Origin::signed(3), 4, 500, RewardDestination::default()));
		assert_ok!(Staking::nominate(Origin::signed(4), vec![11, 21, 41]));

		// New era => election algorithm will trigger
		System::set_block_number(1);
		Session::check_rotate_session(System::block_number());

		assert_eq_uvec!(Session::validators(), vec![20, 10]);

		// with stake 1666 and 1333 respectively
		assert_eq!(Staking::stakers(11).own, 1000);
		assert_eq!(Staking::stakers(11).total, 1000 + 332);
		assert_eq!(Staking::stakers(21).own, 1000);
		assert_eq!(Staking::stakers(21).total, 1000 + 666);

		// Nominator's stake distribution.
		assert_eq!(Staking::stakers(11).others.iter().map(|e| e.value).collect::<Vec<BalanceOf<Test>>>(), vec![166, 166]);
		assert_eq!(Staking::stakers(11).others.iter().map(|e| e.value).sum::<BalanceOf<Test>>(), 332);
		assert_eq!(Staking::stakers(11).others.iter().map(|e| e.who).collect::<Vec<BalanceOf<Test>>>(), vec![3, 1]);

		assert_eq!(Staking::stakers(21).others.iter().map(|e| e.value).collect::<Vec<BalanceOf<Test>>>(), vec![333, 333]);
		assert_eq!(Staking::stakers(21).others.iter().map(|e| e.value).sum::<BalanceOf<Test>>(), 666);
		assert_eq!(Staking::stakers(21).others.iter().map(|e| e.who).collect::<Vec<BalanceOf<Test>>>(), vec![3, 1]);
		check_exposure_all();
	});
}

#[test]
fn phragmen_poc_2_works() {
	// tests the encapsulated phragmen::elect function.
	// Votes  [
	// 	('10', 1000, ['10']),
	// 	('20', 1000, ['20']),
	// 	('30', 1000, ['30']),
	// 	('2', 50, ['10', '20']),
	// 	('4', 1000, ['10', '30'])
	// ]
	// Sequential Phragmén gives
	// 10  is elected with stake  1705.7377049180327 and score  0.0004878048780487805
	// 30  is elected with stake  1344.2622950819673 and score  0.0007439024390243903
	with_externalities(&mut ExtBuilder::default().nominate(false).build(), || {
		// initial setup of 10 and 20, both validators
		assert_eq_uvec!(Session::validators(), vec![20, 10]);

		// Bond [30, 31] as the third validator
		assert_ok!(Staking::bond_extra(Origin::signed(31), 999));
		assert_ok!(Staking::validate(Origin::signed(30), ValidatorPrefs::default()));

		// bond [2,1](A), [4,3](B), as 2 nominators
		for i in &[1, 3] { let _ = Balances::deposit_creating(i, 2000); }

		assert_ok!(Staking::bond(Origin::signed(1), 2, 50, RewardDestination::default()));
		assert_ok!(Staking::nominate(Origin::signed(2), vec![11, 21]));

		assert_ok!(Staking::bond(Origin::signed(3), 4, 1000, RewardDestination::default()));
		assert_ok!(Staking::nominate(Origin::signed(4), vec![11, 31]));

		let winners = phragmen::elect::<Test, _, _, _>(
			2,
			Staking::minimum_validator_count() as usize,
			<Validators<Test>>::enumerate(),
			<Nominators<Test>>::enumerate(),
			Staking::slashable_balance_of,
		);

		let (winners, assignment) = winners.unwrap();

		// 10 and 30 must be the winners
		assert_eq!(winners, vec![11, 31]);
		assert_eq!(assignment, vec![
			(3, vec![(11, 2816371998), (31, 1478595298)]),
			(1, vec![(11, 4294967296)]),
		]);
		check_exposure_all();
	})
}

#[test]
fn switching_roles() {
	// Test that it should be possible to switch between roles (nominator, validator, idle) with minimal overhead.
	with_externalities(&mut ExtBuilder::default()
		.nominate(false)
		.sessions_per_era(3)
		.build(),
	|| {
		// Reset reward destination
		for i in &[10, 20] { assert_ok!(Staking::set_payee(Origin::signed(*i), RewardDestination::Controller)); }

		assert_eq_uvec!(Session::validators(), 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
		System::set_block_number(1);
		Session::check_rotate_session(System::block_number());

		// no change
		assert_eq_uvec!(Session::validators(), vec![20, 10]);

		// new block
		System::set_block_number(2);
		Session::check_rotate_session(System::block_number());

		// no change
		assert_eq_uvec!(Session::validators(), vec![20, 10]);

		// new block --> ne era --> new validators
		System::set_block_number(3);
		Session::check_rotate_session(System::block_number());

		// with current nominators 10 and 5 have the most stake
		assert_eq_uvec!(Session::validators(), 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 + 500 vote
		// 6 : 1000 self vote
		// 2 : 2000 self vote + 500 vote.
		// Winners: 20 and 2

		System::set_block_number(4);
		Session::check_rotate_session(System::block_number());
		assert_eq_uvec!(Session::validators(), vec![6, 10]);

		System::set_block_number(5);
		Session::check_rotate_session(System::block_number());
		assert_eq_uvec!(Session::validators(), vec![6, 10]);

		// ne era
		System::set_block_number(6);
		Session::check_rotate_session(System::block_number());
		assert_eq_uvec!(Session::validators(), vec![2, 20]);
		check_exposure_all();
	});
}

#[test]
fn wrong_vote_is_null() {
	with_externalities(&mut ExtBuilder::default()
		.nominate(false)
		.validator_pool(true)
	.build(),
	|| {
		assert_eq_uvec!(Session::validators(), 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
		System::set_block_number(1);
		Session::check_rotate_session(System::block_number());

		assert_eq_uvec!(Session::validators(), 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.
	with_externalities(&mut ExtBuilder::default()
	.validator_count(3)
	.nominate(false)
	.minimum_validator_count(1)
	.build(), || {
		// setup
		assert_ok!(Staking::set_payee(Origin::signed(10), RewardDestination::Controller));
		let _ = Balances::deposit_creating(&3, 1000);
		let initial_balance_2 = Balances::free_balance(&2);
		let initial_balance_4 = Balances::free_balance(&4);

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

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

		// Not elected even though we want 3.
		assert_eq_uvec!(Session::validators(), vec![30, 20, 10]);

		// min of 10, 20 and 30 (30 got a payout into staking so it raised it from 1 to 11).
		assert_eq!(Staking::slot_stake(), 11);

		// let's make the stingy one elected.
		assert_ok!(Staking::bond(Origin::signed(3), 4, 500, RewardDestination::Controller));
		assert_ok!(Staking::nominate(Origin::signed(4), vec![1]));

		// no rewards paid to 2 and 4 yet
		assert_eq!(Balances::free_balance(&2), initial_balance_2);
		assert_eq!(Balances::free_balance(&4), initial_balance_4);

		System::set_block_number(2);
		Session::check_rotate_session(System::block_number());

		// Stingy one is selected
		assert_eq_uvec!(Session::validators(), vec![20, 10, 2]);
		assert_eq!(Staking::stakers(1), Exposure { own: 1, total: 501, others: vec![IndividualExposure { who: 3, value: 500}]});
		// New slot stake.
		assert_eq!(Staking::slot_stake(), 501);

		// no rewards paid to 2 and 4 yet
		assert_eq!(Balances::free_balance(&2), initial_balance_2);
		assert_eq!(Balances::free_balance(&4), initial_balance_4);

		System::set_block_number(3);
		Session::check_rotate_session(System::block_number());

		let reward = Staking::current_session_reward();
		// 2 will not get a reward of only 1
		// 4 will get the rest
		assert_eq!(Balances::free_balance(&2), initial_balance_2 + 1);
		assert_eq!(Balances::free_balance(&4), initial_balance_4 + reward - 1);
	});
}

#[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.
	with_externalities(&mut ExtBuilder::default()
		.validator_count(3)
		.nominate(false)
		.minimum_validator_count(1)
		.build(),
	|| {

		// setup
		assert_ok!(Staking::chill(Origin::signed(30)));
		assert_ok!(Staking::set_payee(Origin::signed(10), RewardDestination::Controller));
		let initial_balance_2 = Balances::free_balance(&2);
		let initial_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()));

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

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

		// Old ones are rewarded.
		assert_eq!(Balances::free_balance(&10), initial_balance_10 + 10);
		// no rewards paid to 2. This was initial election.
		assert_eq!(Balances::free_balance(&2), initial_balance_2);

		System::set_block_number(2);
		Session::check_rotate_session(System::block_number());

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

		let reward = Staking::current_session_reward();
		// 2 will not get the full reward, practically 1
		assert_eq!(Balances::free_balance(&2), initial_balance_2 + reward.max(1));
		// same for 10
		assert_eq!(Balances::free_balance(&10), initial_balance_10 + 10 + reward.max(1));
		check_exposure_all();
	});
}


#[test]
#[ignore] // Enable this once post-processing is on.
fn phragmen_linear_worse_case_equalize() {
	with_externalities(&mut ExtBuilder::default()
		.nominate(false)
		.validator_pool(true)
		.fair(true)
		.build(),
	|| {
		for i in &[10, 20, 30, 40] { assert_ok!(Staking::set_payee(Origin::signed(*i), RewardDestination::Controller)); }

		bond_validator(50, 1000);
		bond_validator(60, 1000);
		bond_validator(70, 1000);

		bond_nominator(2, 2000, vec![11]);
		bond_nominator(4, 1000, vec![11, 21]);
		bond_nominator(6, 1000, vec![21, 31]);
		bond_nominator(8, 1000, vec![31, 41]);
		bond_nominator(110, 1000, vec![41, 51]);
		bond_nominator(120, 1000, vec![51, 61]);
		bond_nominator(130, 1000, vec![61, 71]);

		assert_eq_uvec!(Session::validators(), vec![40, 30]);
		assert_ok!(Staking::set_validator_count(7));

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

		assert_eq_uvec!(Session::validators(), vec![10, 60, 40, 20, 50, 30, 70]);

		// Sequential Phragmén with post processing gives
		// 10  is elected with stake  3000.0 and score  0.00025
		// 20  is elected with stake  2017.7421569824219 and score  0.0005277777777777777
		// 30  is elected with stake  2008.8712884829595 and score  0.0003333333333333333
		// 40  is elected with stake  2000.0001049958742 and score  0.0005555555555555556
		// 50  is elected with stake  2000.0001049958742 and score  0.0003333333333333333
		// 60  is elected with stake  1991.128921508789 and score  0.0004444444444444444
		// 70  is elected with stake  1982.2574230340813 and score  0.0007222222222222222

		check_exposure_all();

		assert_eq!(Staking::stakers(11).total, 3000);
		assert_eq!(Staking::stakers(21).total, 2209);
		assert_eq!(Staking::stakers(31).total, 2027);
		assert_eq!(Staking::stakers(41).total, 2010);
		assert_eq!(Staking::stakers(51).total, 2010);
		assert_eq!(Staking::stakers(61).total, 1998);
		assert_eq!(Staking::stakers(71).total, 1983);
	})
}

#[test]
fn phragmen_chooses_correct_number_of_validators() {
	with_externalities(&mut ExtBuilder::default()
		.nominate(true)
		.validator_pool(true)
		.fair(true)
		.validator_count(1)
		.build(),
	|| {
		assert_eq!(Staking::validator_count(), 1);
		assert_eq!(Session::validators().len(), 1);

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

		assert_eq!(Session::validators().len(), 1);
		check_exposure_all();
	})
}


#[test]
fn phragmen_score_should_be_accurate_on_large_stakes() {
	with_externalities(&mut ExtBuilder::default()
		.nominate(false)
		.build(),
	|| {
		bond_validator(2, u64::max_value());
		bond_validator(4, u64::max_value());
		bond_validator(6, u64::max_value()-1);
		bond_validator(8, u64::max_value()-2);

		System::set_block_number(2);
		Session::check_rotate_session(System::block_number());

		assert_eq!(Session::validators(), vec![4, 2]);
		check_exposure_all();
	})
}

#[test]
fn phragmen_should_not_overflow_validators() {
	with_externalities(&mut ExtBuilder::default()
		.nominate(false)
		.build(),
	|| {
		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]);

		System::set_block_number(2);
		Session::check_rotate_session(System::block_number());

		assert_eq_uvec!(Session::validators(), 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() {
	with_externalities(&mut ExtBuilder::default()
		.nominate(false)
		.build(),
	|| {
		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]);

		System::set_block_number(2);
		Session::check_rotate_session(System::block_number());

		assert_eq_uvec!(Session::validators(), 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() {
	with_externalities(&mut ExtBuilder::default()
		.nominate(false)
		.build(),
	|| {
		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]);

		System::set_block_number(2);
		Session::check_rotate_session(System::block_number());

		assert_eq_uvec!(Session::validators(), 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_large_scale_test() {
	with_externalities(&mut ExtBuilder::default()
		.nominate(false)
		.minimum_validator_count(1)
		.validator_count(20)
		.build(),
	|| {
		let _ = Staking::chill(Origin::signed(10));
		let _ = Staking::chill(Origin::signed(20));
		let _ = Staking::chill(Origin::signed(30));
		let prefix = 200;

		bond_validator(prefix + 2,  1);
		bond_validator(prefix + 4,  100);
		bond_validator(prefix + 6,  1000000);
		bond_validator(prefix + 8,  100000000001000);
		bond_validator(prefix + 10, 100000000002000);
		bond_validator(prefix + 12, 100000000003000);
		bond_validator(prefix + 14, 400000000000000);
		bond_validator(prefix + 16, 400000000001000);
		bond_validator(prefix + 18, 18000000000000000);
		bond_validator(prefix + 20, 20000000000000000);
		bond_validator(prefix + 22, 500000000000100000);
		bond_validator(prefix + 24, 500000000000200000);

		bond_nominator(50, 990000000000000000, vec![
			prefix + 3,
			prefix + 5,
			prefix + 7,
			prefix + 9,
			prefix + 11,
			prefix + 13,
			prefix + 15,
			prefix + 17,
			prefix + 19,
			prefix + 21,
			prefix + 23,
			prefix + 25]
		);

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

		// For manual inspection
		println!("Validators are {:?}", Session::validators());
		println!("Validators are {:#?}",
			Session::validators()
				.iter()
				.map(|v| (v.clone(), Staking::stakers(v+1)))
				.collect::<Vec<(u64, Exposure<u64, u64>)>>()
		);

		// Each exposure => total == own + sum(others)
		check_exposure_all();

		// aside from some error, stake must be divided correctly
		let individual_expo_sum: u128 = Session::validators()
			.iter()
			.map(|v| Staking::stakers(v+1))
			.fold(0u128, |s, v| if v.others.len() > 0 { s + v.others[0].value as u128 } else { s });
		assert!(
			990000000000000000 - individual_expo_sum < 100,
			format!(
				"Nominator stake = {} / SUM(individual expo) = {} / diff = {}",
				990000000000000000u64,
				individual_expo_sum,
				990000000000000000 - individual_expo_sum
			)
		);
	})
}

#[test]
fn phragmen_large_scale_test_2() {
	with_externalities(&mut ExtBuilder::default()
		.nominate(false)
		.minimum_validator_count(1)
		.validator_count(2)
		.build(),
	|| {
		let _ = Staking::chill(Origin::signed(10));
		let _ = Staking::chill(Origin::signed(20));
		let nom_budget: u64 = 1_000_000_000_000_000_000;
		let c_budget: u64 = 4_000_000;

		bond_validator(2, c_budget as u64);
		bond_validator(4, c_budget as u64);

		bond_nominator(50, nom_budget, vec![3, 5]);

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

		// Each exposure => total == own + sum(others)
		check_exposure_all();

		assert_total_expo(3, nom_budget / 2 + c_budget);
		assert_total_expo(5, nom_budget / 2 + c_budget);
	})
}