tests.rs

		assert!(!Session::validators().contains(&11));
		assert!(!<Validators<Test>>::contains_key(11));
	});
}

#[test]
fn slashing_performed_according_exposure() {
	// This test checks that slashing is performed according the exposure (or more precisely,
	// historical exposure), not the current balance.
	ExtBuilder::default().build().execute_with(|| {
		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 11).own, 1000);

		// Handle an offence with a historical exposure.
		on_offence_now(
			&[OffenceDetails {
				offender: (
					11,
					Exposure {
						total: 500,
						own: 500,
						others: vec![],
					},
				),
				reporters: vec![],
			}],
			&[Perbill::from_percent(50)],
		);

		// The stash account should be slashed for 250 (50% of 500).
		assert_eq!(Balances::free_balance(11), 1000 - 250);
	});
}

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

		assert!(<Validators<Test>>::contains_key(11));
		assert!(Session::validators().contains(&11));
		on_offence_now(
			&[OffenceDetails {
				offender: (
					11,
					Staking::eras_stakers(Staking::active_era().unwrap().index, 11),
				),
				reporters: vec![],
			}],
			&[Perbill::from_percent(0)],
		);
		assert_eq!(Staking::force_era(), Forcing::ForceNew);
		assert!(!<Validators<Test>>::contains_key(11));

		start_era(2);

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

		start_era(3);

		// this staker is in a new slashing span now, having re-registered after
		// their prior slash.

		on_offence_in_era(
			&[OffenceDetails {
				offender: (
					11,
					Staking::eras_stakers(Staking::active_era().unwrap().index, 11),
				),
				reporters: vec![],
			}],
			&[Perbill::from_percent(0)],
			1,
		);

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

		on_offence_in_era(
			&[OffenceDetails {
				offender: (
					11,
					Staking::eras_stakers(Staking::active_era().unwrap().index, 11),
				),
				reporters: vec![],
			}],
			// NOTE: A 100% slash here would clean up the account, causing de-registration.
			&[Perbill::from_percent(95)],
			1,
		);

		// or non-zero.
		assert_eq!(Staking::force_era(), Forcing::NotForcing);
		assert!(<Validators<Test>>::contains_key(11));
    assert!(Session::validators().contains(&11));
		assert_ledger_consistent(11);
	});
}

#[test]
fn reporters_receive_their_slice() {
	// This test verifies that the reporters of the offence receive their slice from the slashed
	// amount.
	ExtBuilder::default().build().execute_with(|| {
		// The reporters' reward is calculated from the total exposure.
		let initial_balance = 1125;

		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 11).total, initial_balance);

		on_offence_now(
			&[OffenceDetails {
				offender: (
					11,
					Staking::eras_stakers(Staking::active_era().unwrap().index, 11),
				),
				reporters: vec![1, 2],
			}],
			&[Perbill::from_percent(50)],
		);

		// F1 * (reward_proportion * slash - 0)
		// 50% * (10% * initial_balance / 2)
		let reward = (initial_balance / 20) / 2;
		let reward_each = reward / 2; // split into two pieces.
		assert_eq!(Balances::free_balance(1), 10 + reward_each);
		assert_eq!(Balances::free_balance(2), 20 + reward_each);
		assert_ledger_consistent(11);
	});
}

#[test]
fn subsequent_reports_in_same_span_pay_out_less() {
	// This test verifies that the reporters of the offence receive their slice from the slashed
	// amount.
	ExtBuilder::default().build().execute_with(|| {
		// The reporters' reward is calculated from the total exposure.
		let initial_balance = 1125;

		assert_eq!(Staking::eras_stakers(Staking::active_era().unwrap().index, 11).total, initial_balance);

		on_offence_now(
			&[OffenceDetails {
				offender: (
					11,
					Staking::eras_stakers(Staking::active_era().unwrap().index, 11),
				),
				reporters: vec![1],
			}],
			&[Perbill::from_percent(20)],
		);

		// F1 * (reward_proportion * slash - 0)
		// 50% * (10% * initial_balance * 20%)
		let reward = (initial_balance / 5) / 20;
		assert_eq!(Balances::free_balance(1), 10 + reward);

		on_offence_now(
			&[OffenceDetails {
				offender: (
					11,
					Staking::eras_stakers(Staking::active_era().unwrap().index, 11),
				),
				reporters: vec![1],
			}],
			&[Perbill::from_percent(50)],
		);

		let prior_payout = reward;

		// F1 * (reward_proportion * slash - prior_payout)
		// 50% * (10% * (initial_balance / 2) - prior_payout)
		let reward = ((initial_balance / 20) - prior_payout) / 2;
		assert_eq!(Balances::free_balance(1), 10 + prior_payout + reward);
		assert_ledger_consistent(11);
	});
}

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

		let exposure = Staking::eras_stakers(Staking::active_era().unwrap().index, 21);
		let initial_balance = Staking::slashable_balance_of(&21);

		let nominator_balances: Vec<_> = exposure.others
			.iter().map(|o| Balances::free_balance(&o.who)).collect();

		on_offence_now(
			&[
				OffenceDetails {
					offender: (11, Staking::eras_stakers(Staking::active_era().unwrap().index, 11)),
					reporters: vec![],
				},
				OffenceDetails {
					offender: (21, Staking::eras_stakers(Staking::active_era().unwrap().index, 21)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(50), Perbill::from_percent(20)],
		);

		// The validator 11 hasn't been slashed, but 21 has been.
		assert_eq!(Balances::free_balance(11), 1000);
		// 2000 - (0.2 * initial_balance)
		assert_eq!(Balances::free_balance(21), 2000 - (2 * initial_balance / 10));

		// ensure that nominators were slashed as well.
		for (initial_balance, other) in nominator_balances.into_iter().zip(exposure.others) {
			assert_eq!(
				Balances::free_balance(&other.who),
				initial_balance - (2 * other.value / 10),
			);
		}
		assert_ledger_consistent(11);
		assert_ledger_consistent(21);
	});
}

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

		on_offence_now(
			&[OffenceDetails {
				offender: (
					11,
					Staking::eras_stakers(Staking::active_era().unwrap().index, 11),
				),
				reporters: vec![],
			}],
			&[Perbill::from_percent(0)],
		);

		// The validator hasn't been slashed. The new era is not forced.
		assert_eq!(Balances::free_balance(11), 1000);
		assert_ledger_consistent(11);
	});
}

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

		on_offence_now(
			&[
				OffenceDetails {
					offender: (11, Staking::eras_stakers(Staking::active_era().unwrap().index, 11)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(50)],
		);

		// The validator has been slashed and has been force-chilled.
		assert_eq!(Balances::free_balance(11), 500);
		assert_eq!(Staking::force_era(), Forcing::ForceNew);

		on_offence_now(
			&[
				OffenceDetails {
					offender: (11, Staking::eras_stakers(Staking::active_era().unwrap().index, 11)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(25)],
		);

		// The validator has not been slashed additionally.
		assert_eq!(Balances::free_balance(11), 500);

		on_offence_now(
			&[
				OffenceDetails {
					offender: (11, Staking::eras_stakers(Staking::active_era().unwrap().index, 11)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(60)],
		);

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

#[test]
fn garbage_collection_after_slashing() {
	ExtBuilder::default().existential_deposit(2).build().execute_with(|| {
		assert_eq!(Balances::free_balance(11), 256_000);

		on_offence_now(
			&[
				OffenceDetails {
					offender: (11, Staking::eras_stakers(Staking::active_era().unwrap().index, 11)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(10)],
		);

		assert_eq!(Balances::free_balance(11), 256_000 - 25_600);
		assert!(<Staking as crate::Store>::SlashingSpans::get(&11).is_some());
		assert_eq!(<Staking as crate::Store>::SpanSlash::get(&(11, 0)).amount_slashed(), &25_600);

		on_offence_now(
			&[
				OffenceDetails {
					offender: (11, Staking::eras_stakers(Staking::active_era().unwrap().index, 11)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(100)],
		);

		// validator and nominator slash in era are garbage-collected by era change,
		// so we don't test those here.

		assert_eq!(Balances::free_balance(11), 0);
		assert_eq!(Balances::total_balance(&11), 0);

		assert_ok!(Staking::reap_stash(Origin::NONE, 11));

		assert!(<Staking as crate::Store>::SlashingSpans::get(&11).is_none());
		assert_eq!(<Staking as crate::Store>::SpanSlash::get(&(11, 0)).amount_slashed(), &0);
	})
}

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

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

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

		on_offence_now(
			&[
				OffenceDetails {
					offender: (11, Staking::eras_stakers(Staking::active_era().unwrap().index, 11)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(10)],
		);

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

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

		assert!(<Staking as crate::Store>::ValidatorSlashInEra::get(&now, &11).is_some());
		assert!(<Staking as crate::Store>::NominatorSlashInEra::get(&now, &101).is_some());

		// + 1 because we have to exit the bonding window.
		for era in (0..(BondingDuration::get() + 1)).map(|offset| offset + now + 1) {
			assert!(<Staking as crate::Store>::ValidatorSlashInEra::get(&now, &11).is_some());
			assert!(<Staking as crate::Store>::NominatorSlashInEra::get(&now, &101).is_some());

			start_era(era);
		}

		assert!(<Staking as crate::Store>::ValidatorSlashInEra::get(&now, &11).is_none());
		assert!(<Staking as crate::Store>::NominatorSlashInEra::get(&now, &101).is_none());
	})
}

#[test]
fn slashing_nominators_by_span_max() {
	ExtBuilder::default().build().execute_with(|| {
		start_era(1);
		start_era(2);
		start_era(3);

		assert_eq!(Balances::free_balance(11), 1000);
		assert_eq!(Balances::free_balance(21), 2000);
		assert_eq!(Balances::free_balance(101), 2000);
		assert_eq!(Staking::slashable_balance_of(&21), 1000);


		let exposure_11 = Staking::eras_stakers(Staking::active_era().unwrap().index, 11);
		let exposure_21 = Staking::eras_stakers(Staking::active_era().unwrap().index, 21);
		assert_eq!(Balances::free_balance(101), 2000);
		let nominated_value_11 = exposure_11.others.iter().find(|o| o.who == 101).unwrap().value;
		let nominated_value_21 = exposure_21.others.iter().find(|o| o.who == 101).unwrap().value;

		on_offence_in_era(
			&[
				OffenceDetails {
					offender: (11, Staking::eras_stakers(Staking::active_era().unwrap().index, 11)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(10)],
			2,
		);

		assert_eq!(Balances::free_balance(11), 900);

		let slash_1_amount = Perbill::from_percent(10) * nominated_value_11;
		assert_eq!(Balances::free_balance(101), 2000 - slash_1_amount);

		let expected_spans = vec![
			slashing::SlashingSpan { index: 1, start: 4, length: None },
			slashing::SlashingSpan { index: 0, start: 0, length: Some(4) },
		];

		let get_span = |account| <Staking as crate::Store>::SlashingSpans::get(&account).unwrap();

		assert_eq!(
			get_span(11).iter().collect::<Vec<_>>(),
			expected_spans,
		);

		assert_eq!(
			get_span(101).iter().collect::<Vec<_>>(),
			expected_spans,
		);

		// second slash: higher era, higher value, same span.
		on_offence_in_era(
			&[
				OffenceDetails {
					offender: (21, Staking::eras_stakers(Staking::active_era().unwrap().index, 21)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(30)],
			3,
		);

		// 11 was not further slashed, but 21 and 101 were.
		assert_eq!(Balances::free_balance(11), 900);
		assert_eq!(Balances::free_balance(21), 1700);

		let slash_2_amount = Perbill::from_percent(30) * nominated_value_21;
		assert!(slash_2_amount > slash_1_amount);

		// only the maximum slash in a single span is taken.
		assert_eq!(Balances::free_balance(101), 2000 - slash_2_amount);

		// third slash: in same era and on same validator as first, higher
		// in-era value, but lower slash value than slash 2.
		on_offence_in_era(
			&[
				OffenceDetails {
					offender: (11, Staking::eras_stakers(Staking::active_era().unwrap().index, 11)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(20)],
			2,
		);

		// 11 was further slashed, but 21 and 101 were not.
		assert_eq!(Balances::free_balance(11), 800);
		assert_eq!(Balances::free_balance(21), 1700);

		let slash_3_amount = Perbill::from_percent(20) * nominated_value_21;
		assert!(slash_3_amount < slash_2_amount);
		assert!(slash_3_amount > slash_1_amount);

		// only the maximum slash in a single span is taken.
		assert_eq!(Balances::free_balance(101), 2000 - slash_2_amount);
	});
}

#[test]
fn slashes_are_summed_across_spans() {
	ExtBuilder::default().build().execute_with(|| {
		start_era(1);
		start_era(2);
		start_era(3);

		assert_eq!(Balances::free_balance(21), 2000);
		assert_eq!(Staking::slashable_balance_of(&21), 1000);

		let get_span = |account| <Staking as crate::Store>::SlashingSpans::get(&account).unwrap();

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

		let expected_spans = vec![
			slashing::SlashingSpan { index: 1, start: 4, length: None },
			slashing::SlashingSpan { index: 0, start: 0, length: Some(4) },
		];

		assert_eq!(get_span(21).iter().collect::<Vec<_>>(), expected_spans);
		assert_eq!(Balances::free_balance(21), 1900);

		// 21 has been force-chilled. re-signal intent to validate.
		Staking::validate(Origin::signed(20), Default::default()).unwrap();

		start_era(4);

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

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

		let expected_spans = vec![
			slashing::SlashingSpan { index: 2, start: 5, length: None },
			slashing::SlashingSpan { index: 1, start: 4, length: Some(1) },
			slashing::SlashingSpan { index: 0, start: 0, length: Some(4) },
		];

		assert_eq!(get_span(21).iter().collect::<Vec<_>>(), expected_spans);
		assert_eq!(Balances::free_balance(21), 1810);
	});
}

#[test]
fn deferred_slashes_are_deferred() {
	ExtBuilder::default().slash_defer_duration(2).build().execute_with(|| {
		start_era(1);

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

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

		on_offence_now(
			&[
				OffenceDetails {
					offender: (11, Staking::eras_stakers(Staking::active_era().unwrap().index, 11)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(10)],
		);

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

		start_era(2);

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

		start_era(3);

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

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

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

#[test]
fn remove_deferred() {
	ExtBuilder::default().slash_defer_duration(2).build().execute_with(|| {
		start_era(1);

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

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

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

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

		start_era(2);

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

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

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

		start_era(3);

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

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

		// the first slash for 10% was cancelled, so no effect.
		assert_eq!(Balances::free_balance(11), 1000);
		assert_eq!(Balances::free_balance(101), 2000);

		start_era(5);

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

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

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

#[test]
fn remove_multi_deferred() {
	ExtBuilder::default().slash_defer_duration(2).build().execute_with(|| {
		start_era(1);

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

		let exposure = Staking::eras_stakers(Staking::active_era().unwrap().index, 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(Staking::active_era().unwrap().index, 21)),
					reporters: vec![],
				}
			],
			&[Perbill::from_percent(10)],
		);

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

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

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

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

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

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

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

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

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

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

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

#[test]
fn 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().execute_with(|| {
		let init_balance_10 = Balances::total_balance(&10);
		let init_balance_100 = Balances::total_balance(&100);

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

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

		<Module<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(3000);
		assert!(total_payout_0 > 10); // Test is meaningful if reward something

		start_era(1);

		<Module<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(3000);
		assert!(total_payout_1 > 10); // Test is meaningful if reward something
		assert!(total_payout_1 != total_payout_0);

		start_era(2);

		<Module<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(3000);
		assert!(total_payout_2 > 10); // Test is meaningful if reward something
		assert!(total_payout_2 != total_payout_0);
		assert!(total_payout_2 != total_payout_1);

		start_era(Staking::history_depth() + 1);

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

		// 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 - Staking::history_depth() == 1);
		assert_noop!(
			Staking::payout_validator(Origin::signed(10), 0),
			// Fail: Era out of history
			Error::<Test>::InvalidEraToReward
		);
		assert_ok!(Staking::payout_validator(Origin::signed(10), 1));
		assert_ok!(Staking::payout_validator(Origin::signed(10), 2));
		assert_noop!(
			Staking::payout_validator(Origin::signed(10), 2),
			// Fail: Double claim
			Error::<Test>::InvalidEraToReward
		);
		assert_noop!(
			Staking::payout_validator(Origin::signed(10), active_era),
			// Fail: Era not finished yet
			Error::<Test>::InvalidEraToReward
		);

		assert_noop!(
			Staking::payout_nominator(Origin::signed(100), 0, vec![(11, 0)]),
			// Fail: Era out of history
			Error::<Test>::InvalidEraToReward
		);
		assert_ok!(Staking::payout_nominator(Origin::signed(100), 1, vec![(11, 0)]));
		assert_ok!(Staking::payout_nominator(Origin::signed(100), 2, vec![(11, 0)]));
		assert_noop!(
			Staking::payout_nominator(Origin::signed(100), 2, vec![(11, 0)]),
			// Fail: Double claim
			Error::<Test>::InvalidEraToReward
		);
		assert_noop!(
			Staking::payout_nominator(Origin::signed(100), active_era, vec![(11, 0)]),
			// Fail: Era not finished yet
			Error::<Test>::InvalidEraToReward
		);
		
		// 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().execute_with(|| {
		start_era(1);

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

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

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

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

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

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

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

#[test]
fn six_session_delay() {
	ExtBuilder::default().build().execute_with(|| {
		use pallet_session::SessionManager;

		let val_set = Session::validators();
		let init_session = Session::current_index();
		let init_active_era = Staking::active_era().unwrap().index;
		// 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!(Staking::active_era().unwrap().index, init_active_era);
		<Staking as SessionManager<_>>::end_session(init_session + 1);
		<Staking as SessionManager<_>>::start_session(init_session + 2);
		assert_eq!(Staking::active_era().unwrap().index, 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!(Staking::active_era().unwrap().index, init_active_era + 1);
		<Staking as SessionManager<_>>::end_session(init_session + 3);
		<Staking as SessionManager<_>>::start_session(init_session + 4);
		assert_eq!(Staking::active_era().unwrap().index, init_active_era + 1);
		<Staking as SessionManager<_>>::end_session(init_session + 4);
		<Staking as SessionManager<_>>::start_session(init_session + 5);
		assert_eq!(Staking::active_era().unwrap().index, 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!(Staking::active_era().unwrap().index, 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() {
	// Test:
	// * If nominator nomination is below the $MaxNominatorRewardedPerValidator other nominator
	//   then the nominator can't claim its reward
	// * A nominator can't claim another nominator reward
	ExtBuilder::default().build().execute_with(|| {
		for i in 0..=<Test as Trait>::MaxNominatorRewardedPerValidator::get() {
			let stash = 10_000 + i as u64;
			let controller = 20_000 + i as u64;
			let balance = 10_000 + i as u64;
			Balances::make_free_balance_be(&stash, balance);
			assert_ok!(
				Staking::bond(
					Origin::signed(stash),
					controller,
					balance,
					RewardDestination::Stash
				)
			);
			assert_ok!(Staking::nominate(Origin::signed(controller), vec![11]));
		}
		mock::start_era(1);

		<Module<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(3 * 1000);
		assert!(total_payout_0 > 100); // Test is meaningful if reward something

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

		// nominator 10_000 can't get its reward because exposure is clipped. However it will try
		// to query other people reward.
		assert_ok!(Staking::payout_nominator(Origin::signed(20_000), 1, vec![(11, 0)]));

		// Assert only nominators from 1 to Max are rewarded
		for i in 0..=<Test as Trait>::MaxNominatorRewardedPerValidator::get() {
			let stash = 10_000 + i as u64;
			let balance = 10_000 + i as u64;
			if stash == 10_000 {
				assert!(Balances::free_balance(&stash) == balance);
			} else {
				assert!(Balances::free_balance(&stash) > balance);
			}
		}
	});
}

#[test]
fn set_history_depth_works() {
	ExtBuilder::default().build().execute_with(|| {
		start_era(10);
		Staking::set_history_depth(Origin::ROOT, 20).unwrap();
		assert!(<Staking as Store>::ErasTotalStake::contains_key(10 - 4));
		assert!(<Staking as Store>::ErasTotalStake::contains_key(10 - 5));
		Staking::set_history_depth(Origin::ROOT, 4).unwrap();
		assert!(<Staking as Store>::ErasTotalStake::contains_key(10 - 4));
		assert!(!<Staking as Store>::ErasTotalStake::contains_key(10 - 5));
		Staking::set_history_depth(Origin::ROOT, 3).unwrap();
		assert!(!<Staking as Store>::ErasTotalStake::contains_key(10 - 4));
		assert!(!<Staking as Store>::ErasTotalStake::contains_key(10 - 5));
		Staking::set_history_depth(Origin::ROOT, 8).unwrap();
		assert!(!<Staking as Store>::ErasTotalStake::contains_key(10 - 4));
		assert!(!<Staking as Store>::ErasTotalStake::contains_key(10 - 5));
	});
}