tests.rs

// 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.

use super::*;
use runtime_io::with_externalities;
use phragmen;
use primitives::traits::OnInitialize;
use srml_support::{assert_ok, assert_noop, assert_eq_uvec, EnumerableStorageMap};
use mock::*;
use srml_support::traits::{Currency, ReservableCurrency};

#[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]);

		if cfg!(feature = "equalize") {
			assert_eq!(
				Staking::stakers(11),
				Exposure { total: 1250, own: 1000, others: vec![ IndividualExposure { who: 101, value: 250 }] }
			);
			assert_eq!(
				Staking::stakers(21),
				Exposure { total: 1250, own: 1000, others: vec![ IndividualExposure { who: 101, value: 250 }] }
			);
			// initial slot_stake
			assert_eq!(Staking::slot_stake(),  1250);
		} else {
			assert_eq!(
				Staking::stakers(11),
				Exposure { total: 1125, own: 1000, others: vec![ IndividualExposure { who: 101, value: 125 }] }
			);
			assert_eq!(
				Staking::stakers(21),
				Exposure { total: 1375, own: 1000, others: vec![ IndividualExposure { who: 101, value: 375 }] }
			);
			// initial slot_stake
			assert_eq!(Staking::slot_stake(),  1125);
		}


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

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

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


		// 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();
		check_nominator_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());
	});
}

#[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));

		start_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());
	});
}

#[test]
fn offline_should_slash_and_disable() {
	// 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);
		// Account 10 is not yet disabled.
		assert!(!is_disabled(10));
		// 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 disabled.
		assert!(is_disabled(10));
	});
}

#[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!(is_disabled(10));
	});
}


#[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::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::on_initialize(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()
	.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::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::on_initialize(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::on_initialize(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::on_initialize(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)/2);
		assert_eq!(Balances::total_balance(&2), 500 + (3*session_reward)/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()
		.nominate(false)
		.build(),
	|| {
		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));

		start_session(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);

		start_session(2);

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

		start_session(3);

		// 1 + sum of of the session rewards accumulated
		let recorded_balance = 1 + 3*session_reward;
		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:
		start_session(5);

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

		// new era is triggered here.
		start_session(6);

		// 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()
		.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]);

		// 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::on_initialize(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::on_initialize(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::on_initialize(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::on_initialize(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::on_initialize(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::on_initialize(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]);

		start_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();
		check_nominator_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::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::on_initialize(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]));

		start_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 + 3 * session_reward);
		assert_eq!(Balances::total_balance(&30), 1 + 3 * session_reward);

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

		if cfg!(feature = "equalize") {
			// 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 + 999);
			// 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![599, 400]
			);
			assert_eq!(
				Staking::stakers(11).others.iter().map(|e| e.who).collect::<Vec<u64>>(),
				vec![3, 1]
			);
			// total expo of 20, with 500 coming from nominators (externals), according to phragmen.
			assert_eq!(Staking::stakers(21).own, 1000);
			assert_eq!(Staking::stakers(21).total, 1000 + 999);
			// 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![400, 599]
			);
			assert_eq!(
				Staking::stakers(21).others.iter().map(|e| e.who).collect::<Vec<u64>>(),
				vec![3, 1]
			);
		} else {
			// total expo of 10, with 1200 coming from nominators (externals), according to phragmen.
			assert_eq!(Staking::stakers(11).own, 1000);
			assert_eq!(Staking::stakers(11).total, 1000 + 800);
			// 2 and 4 supported 10, each with stake 600, according to phragmen.
			assert_eq!(
				Staking::stakers(11).others.iter().map(|e| e.value).collect::<Vec<BalanceOf<Test>>>(),
				vec![400, 400]
			);
			assert_eq!(
				Staking::stakers(11).others.iter().map(|e| e.who).collect::<Vec<u64>>(),
				vec![3, 1]
			);
			// total expo of 20, with 500 coming from nominators (externals), according to phragmen.
			assert_eq!(Staking::stakers(21).own, 1000);
			assert_eq!(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<u64>>(),
				vec![3, 1]
			);
		}

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


		start_era(2);
		// next session reward.
		let new_session_reward = Staking::session_reward() * 3 * Staking::slot_stake();

		let approximation = 3;
		if cfg!(feature = "equalize") {
			// Both have: has [400/2000 ~ 1/5 from 10] + [600/2000 ~ 3/10 from 20]'s reward. ==> 1/5 + 3/10 = 1/2
			assert_eq!(Balances::total_balance(&2), initial_balance + new_session_reward/2 - approximation);
			assert_eq!(Balances::total_balance(&4), initial_balance + new_session_reward/2 - approximation);
			// Rest for validators.
			assert_eq!(Balances::total_balance(&10), initial_balance + new_session_reward/2 + 1);
			assert_eq!(Balances::total_balance(&20), initial_balance + new_session_reward/2 + 1);
		} else {
			// 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) - approximation
			);
			// 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) - approximation
			);

			// 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 + 2);
		}

		check_exposure_all();
		check_nominator_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::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::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,
		start_era(1);

		// 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 + 30 - validator_slash);
		assert_eq!(Balances::total_balance(&2), initial_balance - nominator_slash);
		check_exposure_all();
		check_nominator_all();
		// Because slashing happened.
		assert!(is_disabled(10));
	});
}

#[test]
fn double_staking_should_fail() {
	// should test (in the same order):
	// * an account already bonded as stash cannot be be stashed again.
	// * an account already bonded as stash cannot nominate.
	// * an account already bonded as controller can nominate.
	with_externalities(&mut ExtBuilder::default()
		.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()
		.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()
		.build(),
	|| {
		assert_eq!(Staking::current_era(), 0);

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

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

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

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

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

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

		// Block 7: Era increment.
		start_session(9);
		assert_eq!(Session::current_index(), 9);
		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 = 3 * Staking::current_session_reward(); // 10

		// Move forward the system for payment
		Timestamp::set_timestamp(5);
		start_era(1);

		// Check that RewardDestination is Staked (default)
		assert_eq!(Staking::payee(&11), RewardDestination::Staked);
		// Check that reward went to the stash account of validator
		assert_eq!(Balances::free_balance(&11), 1000 + 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 = 3 * Staking::current_session_reward(); // 1010 (1* slot_stake)

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

		// Move forward the system for payment
		Timestamp::set_timestamp(10);