tests.rs

		// 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);
	});

}

#[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*/);
	});
}

#[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]);
	});
}

#[test]
fn phragmen_election_works_with_post_processing() {
	// 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

	// 10  has load  0.0004878048780487805 and supported
	// 10  with stake  1000.0
	// 20  has load  0 and supported
	// 20  with stake  0
	// 30  has load  0.0007439024390243903 and supported
	// 30  with stake  1000.0
	// 2  has load  0.0004878048780487805 and supported
	// 10  with stake  50.0 20  with stake  0.0
	// 4  has load  0.0007439024390243903 and supported
	// 10  with stake  655.7377049180328 30  with stake  344.26229508196724

	// Sequential Phragmén with post processing gives
	// 10  is elected with stake  1525.0 and score  0.0004878048780487805
	// 30  is elected with stake  1525.0 and score  0.0007439024390243903

	// 10  has load  0.0004878048780487805 and supported
	// 10  with stake  1000.0
	// 20  has load  0 and supported
	// 20  with stake  0
	// 30  has load  0.0007439024390243903 and supported
	// 30  with stake  1000.0
	// 2  has load  0.0004878048780487805 and supported
	// 10  with stake  50.0 20  with stake  0.0
	// 4  has load  0.0007439024390243903 and supported
	// 10  with stake  475.0 30  with stake  525.0
	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,
			ElectionConfig::<BalanceOf<Test>> {
				equalize: true,
				tolerance: <BalanceOf<Test>>::sa(10 as u64),
				iterations: 10,
			}
		);

		let winners = winners.unwrap();

		// 10 and 30 must be the winners
		assert_eq!(winners.iter().map(|w| w.who).collect::<Vec<BalanceOf<Test>>>(), vec![11, 31]);

		let winner_10 = winners.iter().filter(|w| w.who == 11).nth(0).unwrap();
		let winner_30 = winners.iter().filter(|w| w.who == 31).nth(0).unwrap();

		// Check exposures
		assert_eq!(winner_10.exposure.total, 1000 + 525);
		assert_eq!(winner_10.score, PerU128::from_max_value(165991398498018762665060784113057664));
		assert_eq!(winner_10.exposure.others[0].value, 475);
		assert_eq!(winner_10.exposure.others[1].value, 50);

		assert_eq!(winner_30.exposure.total, 1000 + 525);
		assert_eq!(winner_30.score, PerU128::from_max_value(253136882709478613064217695772412937));
		assert_eq!(winner_30.exposure.others[0].value, 525);
	})
}

#[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]);
	});
}

#[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));
	});
}


#[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(),
	|| {
		let bond_validator = |a, b| {
			let _ = Balances::deposit_creating(&(a-1), b);
			assert_ok!(Staking::bond(Origin::signed(a-1), a, b, RewardDestination::Controller));
			assert_ok!(Staking::validate(Origin::signed(a), ValidatorPrefs::default()));
		};
		let bond_nominator = |a, b, v| {
			let _ = Balances::deposit_creating(&(a-1), b);
			assert_ok!(Staking::bond(Origin::signed(a-1), a, b, RewardDestination::Controller));
			assert_ok!(Staking::nominate(Origin::signed(a), v));
		};

		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(112, 1000, vec![51, 61]);
		bond_nominator(114, 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
		// 30  is elected with stake  2008.8712884829595 and score  0.0003333333333333333
		// 50  is elected with stake  2000.0001049958742 and score  0.0003333333333333333
		// 60  is elected with stake  1991.128921508789 and score  0.0004444444444444444
		// 20  is elected with stake  2017.7421569824219 and score  0.0005277777777777777
		// 40  is elected with stake  2000.0001049958742 and score  0.0005555555555555556
		// 70  is elected with stake  1982.2574230340813 and score  0.0007222222222222222

		assert_eq!(Staking::stakers(11).total, 3000);
		assert_eq!(Staking::stakers(31).total, 2035);
		assert_eq!(Staking::stakers(51).total, 2000);
		assert_eq!(Staking::stakers(61).total, 1968);
		assert_eq!(Staking::stakers(21).total, 2035);
		assert_eq!(Staking::stakers(41).total, 2024);
		assert_eq!(Staking::stakers(71).total, 1936);
	})
}

#[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);
	})
}


#[test]
fn phragmen_score_should_be_accurate_on_large_stakes() {
	with_externalities(&mut ExtBuilder::default()
	.nominate(false)
	.build()
	, || {
		let bond_validator = |a, b| {
			assert_ok!(Staking::bond(Origin::signed(a-1), a, b, RewardDestination::Controller));
			assert_ok!(Staking::validate(Origin::signed(a), ValidatorPrefs::default()));
		};

		for i in 1..=8 {
			let _ = Balances::make_free_balance_be(&i, u64::max_value());
		}

		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]);
	})
}

#[test]
fn phragmen_should_not_overflow_validators() {
	with_externalities(&mut ExtBuilder::default()
	.nominate(false)
	.build()
	, || {
		let bond_validator = |a, b| {
			assert_ok!(Staking::bond(Origin::signed(a-1), a, b, RewardDestination::Controller));
			assert_ok!(Staking::validate(Origin::signed(a), ValidatorPrefs::default()));
		};
		let bond_nominator = |a, b, v| {
			assert_ok!(Staking::bond(Origin::signed(a-1), a, b, RewardDestination::Controller));
			assert_ok!(Staking::nominate(Origin::signed(a), v));
		};
		let check_exposure = |a| {
			let expo = Staking::stakers(&a);
			assert_eq!(expo.total, expo.own + expo.others.iter().map(|e| e.value).sum::<u64>());
		};

		for i in 1..=8 {
			let _ = Balances::make_free_balance_be(&i, u64::max_value());
		}

		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![1, 3]);
		bond_nominator(8, u64::max_value()/2, vec![1, 3]);

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

		assert_eq_uvec!(Session::validators(), vec![4, 2]);
		check_exposure(4);
		check_exposure(2);
	})
}

#[test]
fn phragmen_should_not_overflow_nominators() {
	with_externalities(&mut ExtBuilder::default()
	.nominate(false)
	.build()
	, || {
		let bond_validator = |a, b| {
			assert_ok!(Staking::bond(Origin::signed(a-1), a, b, RewardDestination::Controller));
			assert_ok!(Staking::validate(Origin::signed(a), ValidatorPrefs::default()));
		};
		let bond_nominator = |a, b, v| {
			assert_ok!(Staking::bond(Origin::signed(a-1), a, b, RewardDestination::Controller));
			assert_ok!(Staking::nominate(Origin::signed(a), v));
		};
		let check_exposure = |a| {
			let expo = Staking::stakers(&a);
			assert_eq!(expo.total, expo.own + expo.others.iter().map(|e| e.value).sum::<u64>());
		};

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

		for i in 1..=8 {
			let _ = Balances::make_free_balance_be(&i, u64::max_value());
		}

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

		bond_nominator(6, u64::max_value(), vec![1, 3]);
		bond_nominator(8, u64::max_value(), vec![1, 3]);

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

		assert_eq_uvec!(Session::validators(), vec![4, 2]);
		check_exposure(4);
		check_exposure(2);
	})
}

#[test]
fn phragmen_should_not_overflow_ultimate() {
	with_externalities(&mut ExtBuilder::default()
	.nominate(false)
	.build()
	, || {
		let bond_validator = |a, b| {
			assert_ok!(Staking::bond(Origin::signed(a-1), a, b, RewardDestination::Controller));
			assert_ok!(Staking::validate(Origin::signed(a), ValidatorPrefs::default()));
		};
		let bond_nominator = |a, b, v| {
			assert_ok!(Staking::bond(Origin::signed(a-1), a, b, RewardDestination::Controller));
			assert_ok!(Staking::nominate(Origin::signed(a), v));
		};
		let check_exposure = |a| {
			let expo = Staking::stakers(&a);
			assert_eq!(expo.total, expo.own + expo.others.iter().map(|e| e.value).sum::<u64>());
		};

		for i in 1..=8 {
			let _ = Balances::make_free_balance_be(&i, u64::max_value());
		}

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

		bond_nominator(6, u64::max_value(), vec![1, 3]);
		bond_nominator(8, u64::max_value(), vec![1, 3]);

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

		assert_eq_uvec!(Session::validators(), vec![4, 2]);
		check_exposure(4);
		check_exposure(2);
	})
}