tests.rs

		// 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::stakers(&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::stakers(&11)),
					reporters: vec![],
				},
				OffenceDetails {
					offender: (21, Staking::stakers(&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::stakers(&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::stakers(&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::stakers(&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::stakers(&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(1).build().execute_with(|| {
		assert_eq!(Balances::free_balance(&11), 256_000);

		on_offence_now(
			&[
				OffenceDetails {
					offender: (11, Staking::stakers(&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::stakers(&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!(<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::stakers(&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::stakers(&11)),
					reporters: vec![],
				},
			],
			&[Perbill::from_percent(10)],
		);

		let now = Staking::current_era();

		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::stakers(&11);
		let exposure_21 = Staking::stakers(&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::stakers(&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::stakers(&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::stakers(&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::stakers(&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::stakers(&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::stakers(&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::stakers(&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::stakers(&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::stakers(&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::stakers(&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 version_initialized() {
	ExtBuilder::default().build().execute_with(|| {
		assert_eq!(<Staking as Store>::StorageVersion::get(), crate::migration::CURRENT_VERSION);
	});
}