tests.rs

		// no slash yet.
		mock::start_active_era(2);
		assert_eq!(Balances::free_balance(11), 1000);
		assert_eq!(Balances::free_balance(101), 2000);
		assert_eq!(Staking::current_era().unwrap(), 2);
		assert_eq!(active_era(), 2);

		// no slash yet.
		mock::start_active_era(3);
		assert_eq!(Balances::free_balance(11), 1000);
		assert_eq!(Balances::free_balance(101), 2000);
		assert_eq!(Staking::current_era().unwrap(), 3);
		assert_eq!(active_era(), 3);

		// and cannot yet unbond:
		assert_storage_noop!(assert!(
			Staking::withdraw_unbonded(RuntimeOrigin::signed(100), 0).is_ok()
		));
		assert_eq!(
			Ledger::<Test>::get(100).unwrap().unlocking.into_inner(),
			vec![UnlockChunk { era: 4u32, value: 500 as Balance }],
		);

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

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

		// and the leftover of the funds can now be unbonded.
	})
}

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

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

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

		// deferred to start of era 4.
		on_offence_now(
			&[OffenceDetails { offender: (11, exposure.clone()), reporters: vec![] }],
			&[Perbill::from_percent(10)],
		);

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

		mock::start_active_era(2);

		// reported later, but deferred to start of era 4 as well.
		on_offence_in_era(
			&[OffenceDetails { offender: (11, exposure.clone()), reporters: vec![] }],
			&[Perbill::from_percent(15)],
			1,
			DisableStrategy::WhenSlashed,
		);

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

		// cancel one of them.
		assert_ok!(Staking::cancel_deferred_slash(RuntimeOrigin::root(), 4, vec![0]));

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

		mock::start_active_era(3);

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

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

		// the first slash for 10% was cancelled, but the 15% one
		assert_eq!(
			staking_events_since_last_call(),
			vec![
				Event::StakersElected,
				Event::EraPaid(3, 11075, 33225),
				Event::Slashed(11, 50),
				Event::Slashed(101, 7)
			]
		);

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

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

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

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

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

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

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

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

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

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

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

		assert_eq!(<Staking as Store>::UnappliedSlashes::get(&4).len(), 5);

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

		assert_ok!(Staking::cancel_deferred_slash(RuntimeOrigin::root(), 4, vec![0, 2, 4]));

		let slashes = <Staking as Store>::UnappliedSlashes::get(&4);
		assert_eq!(slashes.len(), 2);
		assert_eq!(slashes[0].validator, 21);
		assert_eq!(slashes[1].validator, 42);
	})
}

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

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

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

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

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

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

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

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

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

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

		mock::start_active_era(2);
		let exposure_11 = Staking::eras_stakers(active_era(), &11);
		let exposure_21 = Staking::eras_stakers(active_era(), &21);

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

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

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

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

		// offence with no slash associated
		on_offence_now(
			&[OffenceDetails { offender: (11, exposure_11.clone()), reporters: vec![] }],
			&[Perbill::zero()],
		);

		// offence that slashes 25% of the bond
		on_offence_now(
			&[OffenceDetails { offender: (21, exposure_21.clone()), reporters: vec![] }],
			&[Perbill::from_percent(25)],
		);

		// the offence for validator 10 wasn't slashable so it wasn't disabled
		assert!(!is_disabled(10));
		// whereas validator 20 gets disabled
		assert!(is_disabled(20));
	});
}

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

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

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

		// offence with no slash associated, BUT disabling
		on_offence_in_era(
			&[OffenceDetails { offender: (11, exposure_11.clone()), reporters: vec![] }],
			&[Perbill::zero()],
			now,
			DisableStrategy::Always,
		);

		// offence that slashes 25% of the bond, BUT not disabling
		on_offence_in_era(
			&[OffenceDetails { offender: (21, exposure_21.clone()), reporters: vec![] }],
			&[Perbill::from_percent(25)],
			now,
			DisableStrategy::Never,
		);

		// the offence for validator 10 was explicitly disabled
		assert!(is_disabled(10));
		// whereas validator 20 is explicitly not disabled
		assert!(!is_disabled(20));
	});
}

#[test]
fn offence_threshold_triggers_new_era() {
	ExtBuilder::default()
		.validator_count(4)
		.set_status(41, StakerStatus::Validator)
		.build_and_execute(|| {
			mock::start_active_era(1);
			assert_eq_uvec!(Session::validators(), vec![11, 21, 31, 41]);

			assert_eq!(
				<Test as Config>::OffendingValidatorsThreshold::get(),
				Perbill::from_percent(75),
			);

			// we have 4 validators and an offending validator threshold of 75%,
			// once the third validator commits an offence a new era should be forced

			let exposure_11 = Staking::eras_stakers(Staking::active_era().unwrap().index, &11);
			let exposure_21 = Staking::eras_stakers(Staking::active_era().unwrap().index, &21);
			let exposure_31 = Staking::eras_stakers(Staking::active_era().unwrap().index, &31);

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

			assert_eq!(ForceEra::<Test>::get(), Forcing::NotForcing);

			on_offence_now(
				&[OffenceDetails { offender: (21, exposure_21.clone()), reporters: vec![] }],
				&[Perbill::zero()],
			);

			assert_eq!(ForceEra::<Test>::get(), Forcing::NotForcing);

			on_offence_now(
				&[OffenceDetails { offender: (31, exposure_31.clone()), reporters: vec![] }],
				&[Perbill::zero()],
			);

			assert_eq!(ForceEra::<Test>::get(), Forcing::ForceNew);
		});
}

#[test]
fn disabled_validators_are_kept_disabled_for_whole_era() {
	ExtBuilder::default()
		.validator_count(4)
		.set_status(41, StakerStatus::Validator)
		.build_and_execute(|| {
			mock::start_active_era(1);
			assert_eq_uvec!(Session::validators(), vec![11, 21, 31, 41]);
			assert_eq!(<Test as Config>::SessionsPerEra::get(), 3);

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

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

			on_offence_now(
				&[OffenceDetails { offender: (21, exposure_21.clone()), reporters: vec![] }],
				&[Perbill::from_percent(25)],
			);

			// validator 10 should not be disabled since the offence wasn't slashable
			assert!(!is_disabled(10));
			// validator 20 gets disabled since it got slashed
			assert!(is_disabled(20));

			advance_session();

			// disabled validators should carry-on through all sessions in the era
			assert!(!is_disabled(10));
			assert!(is_disabled(20));

			// validator 10 should now get disabled
			on_offence_now(
				&[OffenceDetails { offender: (11, exposure_11.clone()), reporters: vec![] }],
				&[Perbill::from_percent(25)],
			);

			advance_session();

			// and both are disabled in the last session of the era
			assert!(is_disabled(10));
			assert!(is_disabled(20));

			mock::start_active_era(2);

			// when a new era starts disabled validators get cleared
			assert!(!is_disabled(10));
			assert!(!is_disabled(20));
		});
}

#[test]
fn claim_reward_at_the_last_era_and_no_double_claim_and_invalid_claim() {
	// should check that:
	// * rewards get paid until history_depth for both validators and nominators
	// * an invalid era to claim doesn't update last_reward
	// * double claim of one era fails
	ExtBuilder::default().nominate(true).build_and_execute(|| {
		// Consumed weight for all payout_stakers dispatches that fail
		let err_weight = <Test as Config>::WeightInfo::payout_stakers_alive_staked(0);

		let init_balance_10 = Balances::total_balance(&10);
		let init_balance_100 = Balances::total_balance(&100);

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

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

		Pallet::<Test>::reward_by_ids(vec![(11, 1)]);
		// Compute total payout now for whole duration as other parameter won't change
		let total_payout_0 = current_total_payout_for_duration(reward_time_per_era());

		mock::start_active_era(1);

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

		mock::start_active_era(2);

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

		mock::start_active_era(HistoryDepth::get() + 1);

		let active_era = active_era();

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

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

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

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

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

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

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

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

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

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

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

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

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

		let val_set = Session::validators();
		let init_session = Session::current_index();
		let init_active_era = active_era();

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

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

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

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

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

		<Staking as SessionManager<_>>::end_session(init_session + 3);
		<Staking as SessionManager<_>>::start_session(init_session + 4);
		assert_eq!(active_era(), init_active_era + 1);

		<Staking as SessionManager<_>>::end_session(init_session + 4);
		<Staking as SessionManager<_>>::start_session(init_session + 5);
		assert_eq!(active_era(), init_active_era + 1);

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

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

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

#[test]
fn test_max_nominator_rewarded_per_validator_and_cant_steal_someone_else_reward() {
	ExtBuilder::default().build_and_execute(|| {
		for i in 0..=<<Test as Config>::MaxNominatorRewardedPerValidator as Get<_>>::get() {
			let stash = 10_000 + i as AccountId;
			let controller = 20_000 + i as AccountId;
			let balance = 10_000 + i as Balance;
			Balances::make_free_balance_be(&stash, balance);
			assert_ok!(Staking::bond(
				RuntimeOrigin::signed(stash),
				controller,
				balance,
				RewardDestination::Stash
			));
			assert_ok!(Staking::nominate(RuntimeOrigin::signed(controller), vec![11]));
		}
		mock::start_active_era(1);

		Pallet::<Test>::reward_by_ids(vec![(11, 1)]);
		// compute and ensure the reward amount is greater than zero.
		let _ = current_total_payout_for_duration(reward_time_per_era());

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

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

#[test]
fn test_payout_stakers() {
	// Test that payout_stakers work in general, including that only the top
	// `T::MaxNominatorRewardedPerValidator` nominators are rewarded.
	ExtBuilder::default().has_stakers(false).build_and_execute(|| {
		let balance = 1000;
		// Track the exposure of the validator and all nominators.
		let mut total_exposure = balance;
		// Track the exposure of the validator and the nominators that will get paid out.
		let mut payout_exposure = balance;
		// Create a validator:
		bond_validator(11, 10, balance); // Default(64)
		assert_eq!(Validators::<Test>::count(), 1);

		// Create nominators, targeting stash of validators
		for i in 0..100 {
			let bond_amount = balance + i as Balance;
			bond_nominator(1000 + i, 100 + i, bond_amount, vec![11]);
			total_exposure += bond_amount;
			if i >= 36 {
				payout_exposure += bond_amount;
			};
		}
		let payout_exposure_part = Perbill::from_rational(payout_exposure, total_exposure);

		mock::start_active_era(1);
		Staking::reward_by_ids(vec![(11, 1)]);

		// compute and ensure the reward amount is greater than zero.
		let payout = current_total_payout_for_duration(reward_time_per_era());
		let actual_paid_out = payout_exposure_part * payout;

		mock::start_active_era(2);

		let pre_payout_total_issuance = Balances::total_issuance();
		RewardOnUnbalanceWasCalled::set(false);
		assert_ok!(Staking::payout_stakers(RuntimeOrigin::signed(1337), 11, 1));
		assert_eq_error_rate!(
			Balances::total_issuance(),
			pre_payout_total_issuance + actual_paid_out,
			1
		);
		assert!(RewardOnUnbalanceWasCalled::get());

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

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

		for i in 3..16 {
			Staking::reward_by_ids(vec![(11, 1)]);

			// compute and ensure the reward amount is greater than zero.
			let payout = current_total_payout_for_duration(reward_time_per_era());
			let actual_paid_out = payout_exposure_part * payout;
			let pre_payout_total_issuance = Balances::total_issuance();

			mock::start_active_era(i);
			RewardOnUnbalanceWasCalled::set(false);
			assert_ok!(Staking::payout_stakers(RuntimeOrigin::signed(1337), 11, i - 1));
			assert_eq_error_rate!(
				Balances::total_issuance(),
				pre_payout_total_issuance + actual_paid_out,
				1
			);
			assert!(RewardOnUnbalanceWasCalled::get());
		}

		// We track rewards in `claimed_rewards` vec
		assert_eq!(
			Staking::ledger(&10),
			Some(StakingLedger {
				stash: 11,
				total: 1000,
				active: 1000,
				unlocking: Default::default(),
				claimed_rewards: (1..=14).collect::<Vec<_>>().try_into().unwrap()
			})
		);

		let last_era = 99;
		let history_depth = HistoryDepth::get();
		let expected_last_reward_era = last_era - 1;
		let expected_start_reward_era = last_era - history_depth;
		for i in 16..=last_era {
			Staking::reward_by_ids(vec![(11, 1)]);
			// compute and ensure the reward amount is greater than zero.
			let _ = current_total_payout_for_duration(reward_time_per_era());
			mock::start_active_era(i);
		}

		// We clean it up as history passes
		assert_ok!(Staking::payout_stakers(
			RuntimeOrigin::signed(1337),
			11,
			expected_start_reward_era
		));
		assert_ok!(Staking::payout_stakers(
			RuntimeOrigin::signed(1337),
			11,
			expected_last_reward_era
		));
		assert_eq!(
			Staking::ledger(&10),
			Some(StakingLedger {
				stash: 11,
				total: 1000,
				active: 1000,
				unlocking: Default::default(),
				claimed_rewards: bounded_vec![expected_start_reward_era, expected_last_reward_era]
			})
		);

		// Out of order claims works.
		assert_ok!(Staking::payout_stakers(RuntimeOrigin::signed(1337), 11, 69));
		assert_ok!(Staking::payout_stakers(RuntimeOrigin::signed(1337), 11, 23));
		assert_ok!(Staking::payout_stakers(RuntimeOrigin::signed(1337), 11, 42));
		assert_eq!(
			Staking::ledger(&10),
			Some(StakingLedger {
				stash: 11,
				total: 1000,
				active: 1000,
				unlocking: Default::default(),
				claimed_rewards: bounded_vec![
					expected_start_reward_era,
					23,
					42,
					69,
					expected_last_reward_era
				]
			})
		);
	});
}

#[test]
fn payout_stakers_handles_basic_errors() {
	// Here we will test payouts handle all errors.
	ExtBuilder::default().has_stakers(false).build_and_execute(|| {
		// Consumed weight for all payout_stakers dispatches that fail
		let err_weight = <Test as Config>::WeightInfo::payout_stakers_alive_staked(0);

		// Same setup as the test above
		let balance = 1000;
		bond_validator(11, 10, balance); // Default(64)

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

		mock::start_active_era(1);
		Staking::reward_by_ids(vec![(11, 1)]);

		// compute and ensure the reward amount is greater than zero.
		let _ = current_total_payout_for_duration(reward_time_per_era());

		mock::start_active_era(2);

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

		let last_era = 99;
		for i in 3..=last_era {
			Staking::reward_by_ids(vec![(11, 1)]);
			// compute and ensure the reward amount is greater than zero.
			let _ = current_total_payout_for_duration(reward_time_per_era());
			mock::start_active_era(i);
		}

		let history_depth = HistoryDepth::get();
		let expected_last_reward_era = last_era - 1;
		let expected_start_reward_era = last_era - history_depth;

		// We are at era last_era=99. Given history_depth=80, we should be able
		// to payout era starting from expected_start_reward_era=19 through
		// expected_last_reward_era=98 (80 total eras), but not 18 or 99.
		assert_noop!(
			Staking::payout_stakers(RuntimeOrigin::signed(1337), 11, expected_start_reward_era - 1),
			Error::<Test>::InvalidEraToReward.with_weight(err_weight)
		);
		assert_noop!(
			Staking::payout_stakers(RuntimeOrigin::signed(1337), 11, expected_last_reward_era + 1),
			Error::<Test>::InvalidEraToReward.with_weight(err_weight)
		);
		assert_ok!(Staking::payout_stakers(
			RuntimeOrigin::signed(1337),
			11,
			expected_start_reward_era
		));
		assert_ok!(Staking::payout_stakers(
			RuntimeOrigin::signed(1337),
			11,
			expected_last_reward_era
		));

		// Can't claim again
		assert_noop!(
			Staking::payout_stakers(RuntimeOrigin::signed(1337), 11, expected_start_reward_era),
			Error::<Test>::AlreadyClaimed.with_weight(err_weight)
		);
		assert_noop!(
			Staking::payout_stakers(RuntimeOrigin::signed(1337), 11, expected_last_reward_era),
			Error::<Test>::AlreadyClaimed.with_weight(err_weight)
		);
	});
}

#[test]
fn payout_stakers_handles_weight_refund() {
	// Note: this test relies on the assumption that `payout_stakers_alive_staked` is solely used by
	// `payout_stakers` to calculate the weight of each payout op.
	ExtBuilder::default().has_stakers(false).build_and_execute(|| {
		let max_nom_rewarded =
			<<Test as Config>::MaxNominatorRewardedPerValidator as Get<_>>::get();
		// Make sure the configured value is meaningful for our use.
		assert!(max_nom_rewarded >= 4);
		let half_max_nom_rewarded = max_nom_rewarded / 2;
		// Sanity check our max and half max nominator quantities.
		assert!(half_max_nom_rewarded > 0);
		assert!(max_nom_rewarded > half_max_nom_rewarded);

		let max_nom_rewarded_weight =
			<Test as Config>::WeightInfo::payout_stakers_alive_staked(max_nom_rewarded);
		let half_max_nom_rewarded_weight =
			<Test as Config>::WeightInfo::payout_stakers_alive_staked(half_max_nom_rewarded);
		let zero_nom_payouts_weight = <Test as Config>::WeightInfo::payout_stakers_alive_staked(0);
		assert!(zero_nom_payouts_weight.any_gt(Weight::zero()));
		assert!(half_max_nom_rewarded_weight.any_gt(zero_nom_payouts_weight));
		assert!(max_nom_rewarded_weight.any_gt(half_max_nom_rewarded_weight));

		let balance = 1000;
		bond_validator(11, 10, balance);

		// Era 1
		start_active_era(1);

		// Reward just the validator.
		Staking::reward_by_ids(vec![(11, 1)]);

		// Add some `half_max_nom_rewarded` nominators who will start backing the validator in the
		// next era.
		for i in 0..half_max_nom_rewarded {
			bond_nominator((1000 + i).into(), (100 + i).into(), balance + i as Balance, vec![11]);
		}

		// Era 2
		start_active_era(2);

		// Collect payouts when there are no nominators
		let call = TestCall::Staking(StakingCall::payout_stakers { validator_stash: 11, era: 1 });
		let info = call.get_dispatch_info();
		let result = call.dispatch(RuntimeOrigin::signed(20));
		assert_ok!(result);
		assert_eq!(extract_actual_weight(&result, &info), zero_nom_payouts_weight);

		// The validator is not rewarded in this era; so there will be zero payouts to claim for
		// this era.

		// Era 3
		start_active_era(3);

		// Collect payouts for an era where the validator did not receive any points.
		let call = TestCall::Staking(StakingCall::payout_stakers { validator_stash: 11, era: 2 });
		let info = call.get_dispatch_info();
		let result = call.dispatch(RuntimeOrigin::signed(20));
		assert_ok!(result);
		assert_eq!(extract_actual_weight(&result, &info), zero_nom_payouts_weight);

		// Reward the validator and its nominators.
		Staking::reward_by_ids(vec![(11, 1)]);

		// Era 4
		start_active_era(4);

		// Collect payouts when the validator has `half_max_nom_rewarded` nominators.
		let call = TestCall::Staking(StakingCall::payout_stakers { validator_stash: 11, era: 3 });
		let info = call.get_dispatch_info();
		let result = call.dispatch(RuntimeOrigin::signed(20));
		assert_ok!(result);
		assert_eq!(extract_actual_weight(&result, &info), half_max_nom_rewarded_weight);

		// Add enough nominators so that we are at the limit. They will be active nominators
		// in the next era.
		for i in half_max_nom_rewarded..max_nom_rewarded {
			bond_nominator((1000 + i).into(), (100 + i).into(), balance + i as Balance, vec![11]);
		}

		// Era 5
		start_active_era(5);
		// We now have `max_nom_rewarded` nominators actively nominating our validator.

		// Reward the validator so we can collect for everyone in the next era.
		Staking::reward_by_ids(vec![(11, 1)]);

		// Era 6
		start_active_era(6);

		// Collect payouts when the validator had `half_max_nom_rewarded` nominators.
		let call = TestCall::Staking(StakingCall::payout_stakers { validator_stash: 11, era: 5 });
		let info = call.get_dispatch_info();
		let result = call.dispatch(RuntimeOrigin::signed(20));
		assert_ok!(result);
		assert_eq!(extract_actual_weight(&result, &info), max_nom_rewarded_weight);

		// Try and collect payouts for an era that has already been collected.
		let call = TestCall::Staking(StakingCall::payout_stakers { validator_stash: 11, era: 5 });
		let info = call.get_dispatch_info();
		let result = call.dispatch(RuntimeOrigin::signed(20));
		assert!(result.is_err());
		// When there is an error the consumed weight == weight when there are 0 nominator payouts.
		assert_eq!(extract_actual_weight(&result, &info), zero_nom_payouts_weight);
	});
}

#[test]
fn bond_during_era_correctly_populates_claimed_rewards() {
	ExtBuilder::default().has_stakers(false).build_and_execute(|| {
		// Era = None
		bond_validator(9, 8, 1000);
		assert_eq!(
			Staking::ledger(&8),
			Some(StakingLedger {
				stash: 9,
				total: 1000,
				active: 1000,
				unlocking: Default::default(),
				claimed_rewards: bounded_vec![],
			})
		);
		mock::start_active_era(5);
		bond_validator(11, 10, 1000);
		assert_eq!(
			Staking::ledger(&10),
			Some(StakingLedger {
				stash: 11,
				total: 1000,
				active: 1000,
				unlocking: Default::default(),
				claimed_rewards: (0..5).collect::<Vec<_>>().try_into().unwrap(),
			})
		);

		// make sure only era upto history depth is stored
		let current_era = 99;
		let last_reward_era = 99 - HistoryDepth::get();
		mock::start_active_era(current_era);
		bond_validator(13, 12, 1000);
		assert_eq!(
			Staking::ledger(&12),
			Some(StakingLedger {
				stash: 13,
				total: 1000,
				active: 1000,
				unlocking: Default::default(),
				claimed_rewards: (last_reward_era..current_era)
					.collect::<Vec<_>>()
					.try_into()
					.unwrap(),
			})
		);
	});
}

#[test]
fn offences_weight_calculated_correctly() {
	ExtBuilder::default().nominate(true).build_and_execute(|| {