paras.rs

			check_code_is_stored(&validation_code);

			run_to_block(pruned_at, None);
			assert!(<Paras as Store>::PastCodeHash::get(&(id, at_block)).is_none());
			assert!(Paras::past_code_meta(&id).most_recent_change().is_none());
			check_code_is_not_stored(&validation_code);
		});
	}

	#[test]
	fn note_new_head_sets_head() {
		let code_retention_period = 10;
		let paras = vec![(
			0u32.into(),
			ParaGenesisArgs {
				parachain: true,
				genesis_head: dummy_head_data(),
				validation_code: dummy_validation_code(),
			},
		)];

		let genesis_config = MockGenesisConfig {
			paras: GenesisConfig { paras, ..Default::default() },
			configuration: crate::configuration::GenesisConfig {
				config: HostConfiguration { code_retention_period, ..Default::default() },
				..Default::default()
			},
			..Default::default()
		};

		new_test_ext(genesis_config).execute_with(|| {
			let id_a = ParaId::from(0u32);

			assert_eq!(Paras::para_head(&id_a), Some(dummy_head_data()));

			Paras::note_new_head(id_a, vec![1, 2, 3].into(), 0);

			assert_eq!(Paras::para_head(&id_a), Some(vec![1, 2, 3].into()));
		});
	}

	#[test]
	fn note_past_code_sets_up_pruning_correctly() {
		let code_retention_period = 10;
		let paras = vec![
			(
				0u32.into(),
				ParaGenesisArgs {
					parachain: true,
					genesis_head: dummy_head_data(),
					validation_code: dummy_validation_code(),
				},
			),
			(
				1u32.into(),
				ParaGenesisArgs {
					parachain: false,
					genesis_head: dummy_head_data(),
					validation_code: dummy_validation_code(),
				},
			),
		];

		let genesis_config = MockGenesisConfig {
			paras: GenesisConfig { paras, ..Default::default() },
			configuration: crate::configuration::GenesisConfig {
				config: HostConfiguration { code_retention_period, ..Default::default() },
				..Default::default()
			},
			..Default::default()
		};

		new_test_ext(genesis_config).execute_with(|| {
			let id_a = ParaId::from(0u32);
			let id_b = ParaId::from(1u32);

			Paras::note_past_code(id_a, 10, 12, ValidationCode(vec![1, 2, 3]).hash());
			Paras::note_past_code(id_b, 20, 23, ValidationCode(vec![4, 5, 6]).hash());

			assert_eq!(<Paras as Store>::PastCodePruning::get(), vec![(id_a, 12), (id_b, 23)]);
			assert_eq!(
				Paras::past_code_meta(&id_a),
				ParaPastCodeMeta { upgrade_times: vec![upgrade_at(10, 12)], last_pruned: None }
			);
			assert_eq!(
				Paras::past_code_meta(&id_b),
				ParaPastCodeMeta { upgrade_times: vec![upgrade_at(20, 23)], last_pruned: None }
			);
		});
	}

	#[test]
	fn code_upgrade_applied_after_delay() {
		let code_retention_period = 10;
		let validation_upgrade_delay = 5;
		let validation_upgrade_frequency = 10;

		let original_code = ValidationCode(vec![1, 2, 3]);
		let paras = vec![(
			0u32.into(),
			ParaGenesisArgs {
				parachain: true,
				genesis_head: dummy_head_data(),
				validation_code: original_code.clone(),
			},
		)];

		let genesis_config = MockGenesisConfig {
			paras: GenesisConfig { paras, ..Default::default() },
			configuration: crate::configuration::GenesisConfig {
				config: HostConfiguration {
					code_retention_period,
					validation_upgrade_delay,
					validation_upgrade_frequency,
					pvf_checking_enabled: false,
					..Default::default()
				},
				..Default::default()
			},
			..Default::default()
		};

		new_test_ext(genesis_config).execute_with(|| {
			check_code_is_stored(&original_code);

			let para_id = ParaId::from(0);
			let new_code = ValidationCode(vec![4, 5, 6]);

			run_to_block(2, None);
			assert_eq!(Paras::current_code(&para_id), Some(original_code.clone()));

			let expected_at = {
				// this parablock is in the context of block 1.
				let expected_at = 1 + validation_upgrade_delay;
				let next_possible_upgrade_at = 1 + validation_upgrade_frequency;
				Paras::schedule_code_upgrade(
					para_id,
					new_code.clone(),
					1,
					&Configuration::config(),
				);
				Paras::note_new_head(para_id, Default::default(), 1);

				assert!(Paras::past_code_meta(&para_id).most_recent_change().is_none());
				assert_eq!(<Paras as Store>::FutureCodeUpgrades::get(&para_id), Some(expected_at));
				assert_eq!(<Paras as Store>::FutureCodeHash::get(&para_id), Some(new_code.hash()));
				assert_eq!(<Paras as Store>::UpcomingUpgrades::get(), vec![(para_id, expected_at)]);
				assert_eq!(
					<Paras as Store>::UpgradeCooldowns::get(),
					vec![(para_id, next_possible_upgrade_at)]
				);
				assert_eq!(Paras::current_code(&para_id), Some(original_code.clone()));
				check_code_is_stored(&original_code);
				check_code_is_stored(&new_code);

				expected_at
			};

			run_to_block(expected_at, None);

			// the candidate is in the context of the parent of `expected_at`,
			// thus does not trigger the code upgrade.
			{
				Paras::note_new_head(para_id, Default::default(), expected_at - 1);

				assert!(Paras::past_code_meta(&para_id).most_recent_change().is_none());
				assert_eq!(<Paras as Store>::FutureCodeUpgrades::get(&para_id), Some(expected_at));
				assert_eq!(<Paras as Store>::FutureCodeHash::get(&para_id), Some(new_code.hash()));
				assert_eq!(
					<Paras as Store>::UpgradeGoAheadSignal::get(&para_id),
					Some(UpgradeGoAhead::GoAhead)
				);
				assert_eq!(Paras::current_code(&para_id), Some(original_code.clone()));
				check_code_is_stored(&original_code);
				check_code_is_stored(&new_code);
			}

			run_to_block(expected_at + 1, None);

			// the candidate is in the context of `expected_at`, and triggers
			// the upgrade.
			{
				Paras::note_new_head(para_id, Default::default(), expected_at);

				assert_eq!(Paras::past_code_meta(&para_id).most_recent_change(), Some(expected_at));
				assert_eq!(
					<Paras as Store>::PastCodeHash::get(&(para_id, expected_at)),
					Some(original_code.hash()),
				);
				assert!(<Paras as Store>::FutureCodeUpgrades::get(&para_id).is_none());
				assert!(<Paras as Store>::FutureCodeHash::get(&para_id).is_none());
				assert!(<Paras as Store>::UpgradeGoAheadSignal::get(&para_id).is_none());
				assert_eq!(Paras::current_code(&para_id), Some(new_code.clone()));
				check_code_is_stored(&original_code);
				check_code_is_stored(&new_code);
			}
		});
	}

	#[test]
	fn code_upgrade_applied_after_delay_even_when_late() {
		let code_retention_period = 10;
		let validation_upgrade_delay = 5;
		let validation_upgrade_frequency = 10;

		let original_code = ValidationCode(vec![1, 2, 3]);
		let paras = vec![(
			0u32.into(),
			ParaGenesisArgs {
				parachain: true,
				genesis_head: dummy_head_data(),
				validation_code: original_code.clone(),
			},
		)];

		let genesis_config = MockGenesisConfig {
			paras: GenesisConfig { paras, ..Default::default() },
			configuration: crate::configuration::GenesisConfig {
				config: HostConfiguration {
					code_retention_period,
					validation_upgrade_delay,
					validation_upgrade_frequency,
					pvf_checking_enabled: false,
					..Default::default()
				},
				..Default::default()
			},
			..Default::default()
		};

		new_test_ext(genesis_config).execute_with(|| {
			let para_id = ParaId::from(0);
			let new_code = ValidationCode(vec![4, 5, 6]);

			run_to_block(2, None);
			assert_eq!(Paras::current_code(&para_id), Some(original_code.clone()));

			let expected_at = {
				// this parablock is in the context of block 1.
				let expected_at = 1 + validation_upgrade_delay;
				let next_possible_upgrade_at = 1 + validation_upgrade_frequency;
				Paras::schedule_code_upgrade(
					para_id,
					new_code.clone(),
					1,
					&Configuration::config(),
				);
				Paras::note_new_head(para_id, Default::default(), 1);

				assert!(Paras::past_code_meta(&para_id).most_recent_change().is_none());
				assert_eq!(<Paras as Store>::FutureCodeUpgrades::get(&para_id), Some(expected_at));
				assert_eq!(<Paras as Store>::FutureCodeHash::get(&para_id), Some(new_code.hash()));
				assert_eq!(<Paras as Store>::UpcomingUpgrades::get(), vec![(para_id, expected_at)]);
				assert_eq!(
					<Paras as Store>::UpgradeCooldowns::get(),
					vec![(para_id, next_possible_upgrade_at)]
				);
				assert!(<Paras as Store>::UpgradeGoAheadSignal::get(&para_id).is_none());
				assert_eq!(Paras::current_code(&para_id), Some(original_code.clone()));

				expected_at
			};

			run_to_block(expected_at + 1 + 4, None);

			// the candidate is in the context of the first descendant of `expected_at`, and triggers
			// the upgrade.
			{
				// The signal should be set to go-ahead until the new head is actually processed.
				assert_eq!(
					<Paras as Store>::UpgradeGoAheadSignal::get(&para_id),
					Some(UpgradeGoAhead::GoAhead),
				);

				Paras::note_new_head(para_id, Default::default(), expected_at + 4);

				assert_eq!(Paras::past_code_meta(&para_id).most_recent_change(), Some(expected_at));

				assert_eq!(
					<Paras as Store>::PastCodeHash::get(&(para_id, expected_at)),
					Some(original_code.hash()),
				);
				assert!(<Paras as Store>::FutureCodeUpgrades::get(&para_id).is_none());
				assert!(<Paras as Store>::FutureCodeHash::get(&para_id).is_none());
				assert!(<Paras as Store>::UpgradeGoAheadSignal::get(&para_id).is_none());
				assert_eq!(Paras::current_code(&para_id), Some(new_code.clone()));
			}
		});
	}

	#[test]
	fn submit_code_change_when_not_allowed_is_err() {
		let code_retention_period = 10;
		let validation_upgrade_delay = 7;
		let validation_upgrade_frequency = 100;

		let paras = vec![(
			0u32.into(),
			ParaGenesisArgs {
				parachain: true,
				genesis_head: dummy_head_data(),
				validation_code: vec![1, 2, 3].into(),
			},
		)];

		let genesis_config = MockGenesisConfig {
			paras: GenesisConfig { paras, ..Default::default() },
			configuration: crate::configuration::GenesisConfig {
				config: HostConfiguration {
					code_retention_period,
					validation_upgrade_delay,
					validation_upgrade_frequency,
					pvf_checking_enabled: false,
					..Default::default()
				},
				..Default::default()
			},
			..Default::default()
		};

		new_test_ext(genesis_config).execute_with(|| {
			let para_id = ParaId::from(0);
			let new_code = ValidationCode(vec![4, 5, 6]);
			let newer_code = ValidationCode(vec![4, 5, 6, 7]);

			run_to_block(1, None);
			Paras::schedule_code_upgrade(para_id, new_code.clone(), 1, &Configuration::config());
			assert_eq!(
				<Paras as Store>::FutureCodeUpgrades::get(&para_id),
				Some(1 + validation_upgrade_delay)
			);
			assert_eq!(<Paras as Store>::FutureCodeHash::get(&para_id), Some(new_code.hash()));
			check_code_is_stored(&new_code);

			// We expect that if an upgrade is signalled while there is already one pending we just
			// ignore it. Note that this is only true from perspective of this module.
			run_to_block(2, None);
			Paras::schedule_code_upgrade(para_id, newer_code.clone(), 2, &Configuration::config());
			assert_eq!(
				<Paras as Store>::FutureCodeUpgrades::get(&para_id),
				Some(1 + validation_upgrade_delay), // did not change since the same assertion from the last time.
			);
			assert_eq!(<Paras as Store>::FutureCodeHash::get(&para_id), Some(new_code.hash()));
			check_code_is_not_stored(&newer_code);
		});
	}

	#[test]
	fn full_parachain_cleanup_storage() {
		let code_retention_period = 20;
		let validation_upgrade_delay = 1 + 5;

		let original_code = ValidationCode(vec![1, 2, 3]);
		let paras = vec![(
			0u32.into(),
			ParaGenesisArgs {
				parachain: true,
				genesis_head: dummy_head_data(),
				validation_code: original_code.clone(),
			},
		)];

		let genesis_config = MockGenesisConfig {
			paras: GenesisConfig { paras, ..Default::default() },
			configuration: crate::configuration::GenesisConfig {
				config: HostConfiguration {
					code_retention_period,
					validation_upgrade_delay,
					pvf_checking_enabled: false,
					minimum_validation_upgrade_delay: 0,
					..Default::default()
				},
				..Default::default()
			},
			..Default::default()
		};

		new_test_ext(genesis_config).execute_with(|| {
			check_code_is_stored(&original_code);

			let para_id = ParaId::from(0);
			let new_code = ValidationCode(vec![4, 5, 6]);

			run_to_block(2, None);
			assert_eq!(Paras::current_code(&para_id), Some(original_code.clone()));
			check_code_is_stored(&original_code);

			let expected_at = {
				// this parablock is in the context of block 1.
				let expected_at = 1 + validation_upgrade_delay;
				Paras::schedule_code_upgrade(
					para_id,
					new_code.clone(),
					1,
					&Configuration::config(),
				);
				Paras::note_new_head(para_id, Default::default(), 1);

				assert!(Paras::past_code_meta(&para_id).most_recent_change().is_none());
				assert_eq!(<Paras as Store>::FutureCodeUpgrades::get(&para_id), Some(expected_at));
				assert_eq!(<Paras as Store>::FutureCodeHash::get(&para_id), Some(new_code.hash()));
				assert_eq!(Paras::current_code(&para_id), Some(original_code.clone()));
				check_code_is_stored(&original_code);
				check_code_is_stored(&new_code);

				expected_at
			};

			// Cannot offboard while an upgrade is pending.
			assert_err!(Paras::schedule_para_cleanup(para_id), Error::<Test>::CannotOffboard);

			// Enact the upgrade.
			//
			// For that run to block #7 and submit a new head.
			assert_eq!(expected_at, 7);
			run_to_block(7, None);
			assert_eq!(<frame_system::Pallet<Test>>::block_number(), 7);
			Paras::note_new_head(para_id, Default::default(), expected_at);

			assert_ok!(Paras::schedule_para_cleanup(para_id));

			// run to block #10, with a 2 session changes at the end of the block 7 & 8 (so 8 and 9
			// observe the new sessions).
			run_to_block(10, Some(vec![8, 9]));

			// cleaning up the parachain should place the current parachain code
			// into the past code buffer & schedule cleanup.
			//
			// Why 7 and 8? See above, the clean up scheduled above was processed at the block 8.
			// The initial upgrade was enacted at the block 7.
			assert_eq!(Paras::past_code_meta(&para_id).most_recent_change(), Some(8));
			assert_eq!(<Paras as Store>::PastCodeHash::get(&(para_id, 8)), Some(new_code.hash()));
			assert_eq!(<Paras as Store>::PastCodePruning::get(), vec![(para_id, 7), (para_id, 8)]);
			check_code_is_stored(&original_code);
			check_code_is_stored(&new_code);

			// any future upgrades haven't been used to validate yet, so those
			// are cleaned up immediately.
			assert!(<Paras as Store>::FutureCodeUpgrades::get(&para_id).is_none());
			assert!(<Paras as Store>::FutureCodeHash::get(&para_id).is_none());
			assert!(Paras::current_code(&para_id).is_none());

			// run to do the final cleanup
			let cleaned_up_at = 8 + code_retention_period + 1;
			run_to_block(cleaned_up_at, None);

			// now the final cleanup: last past code cleaned up, and this triggers meta cleanup.
			assert_eq!(Paras::past_code_meta(&para_id), Default::default());
			assert!(<Paras as Store>::PastCodeHash::get(&(para_id, 7)).is_none());
			assert!(<Paras as Store>::PastCodeHash::get(&(para_id, 8)).is_none());
			assert!(<Paras as Store>::PastCodePruning::get().is_empty());
			check_code_is_not_stored(&original_code);
			check_code_is_not_stored(&new_code);
		});
	}

	#[test]
	fn para_incoming_at_session() {
		let code_a = ValidationCode(vec![2]);
		let code_b = ValidationCode(vec![1]);
		let code_c = ValidationCode(vec![3]);

		let genesis_config = MockGenesisConfig {
			configuration: crate::configuration::GenesisConfig {
				config: HostConfiguration { pvf_checking_enabled: true, ..Default::default() },
				..Default::default()
			},
			..Default::default()
		};

		new_test_ext(genesis_config).execute_with(|| {
			run_to_block(1, Some(vec![1]));

			let b = ParaId::from(525);
			let a = ParaId::from(999);
			let c = ParaId::from(333);

			assert_ok!(Paras::schedule_para_initialize(
				b,
				ParaGenesisArgs {
					parachain: true,
					genesis_head: vec![1].into(),
					validation_code: code_b.clone(),
				},
			));

			assert_ok!(Paras::schedule_para_initialize(
				a,
				ParaGenesisArgs {
					parachain: false,
					genesis_head: vec![2].into(),
					validation_code: code_a.clone(),
				},
			));

			assert_ok!(Paras::schedule_para_initialize(
				c,
				ParaGenesisArgs {
					parachain: true,
					genesis_head: vec![3].into(),
					validation_code: code_c.clone(),
				},
			));

			IntoIterator::into_iter([0, 1, 2, 3])
				.map(|i| PvfCheckStatement {
					accept: true,
					subject: code_a.hash(),
					session_index: 1,
					validator_index: i.into(),
				})
				.for_each(sign_and_include_pvf_check_statement);

			IntoIterator::into_iter([1, 2, 3, 4])
				.map(|i| PvfCheckStatement {
					accept: true,
					subject: code_b.hash(),
					session_index: 1,
					validator_index: i.into(),
				})
				.for_each(sign_and_include_pvf_check_statement);

			IntoIterator::into_iter([0, 2, 3, 4])
				.map(|i| PvfCheckStatement {
					accept: true,
					subject: code_c.hash(),
					session_index: 1,
					validator_index: i.into(),
				})
				.for_each(sign_and_include_pvf_check_statement);

			assert_eq!(
				<Paras as Store>::ActionsQueue::get(Paras::scheduled_session()),
				vec![c, b, a],
			);

			// Lifecycle is tracked correctly
			assert_eq!(<Paras as Store>::ParaLifecycles::get(&a), Some(ParaLifecycle::Onboarding));
			assert_eq!(<Paras as Store>::ParaLifecycles::get(&b), Some(ParaLifecycle::Onboarding));
			assert_eq!(<Paras as Store>::ParaLifecycles::get(&c), Some(ParaLifecycle::Onboarding));

			// run to block without session change.
			run_to_block(2, None);

			assert_eq!(Paras::parachains(), Vec::new());
			assert_eq!(
				<Paras as Store>::ActionsQueue::get(Paras::scheduled_session()),
				vec![c, b, a],
			);

			// Lifecycle is tracked correctly
			assert_eq!(<Paras as Store>::ParaLifecycles::get(&a), Some(ParaLifecycle::Onboarding));
			assert_eq!(<Paras as Store>::ParaLifecycles::get(&b), Some(ParaLifecycle::Onboarding));
			assert_eq!(<Paras as Store>::ParaLifecycles::get(&c), Some(ParaLifecycle::Onboarding));

			// Two sessions pass, so action queue is triggered
			run_to_block(4, Some(vec![3, 4]));

			assert_eq!(Paras::parachains(), vec![c, b]);
			assert_eq!(<Paras as Store>::ActionsQueue::get(Paras::scheduled_session()), Vec::new());

			// Lifecycle is tracked correctly
			assert_eq!(<Paras as Store>::ParaLifecycles::get(&a), Some(ParaLifecycle::Parathread));
			assert_eq!(<Paras as Store>::ParaLifecycles::get(&b), Some(ParaLifecycle::Parachain));
			assert_eq!(<Paras as Store>::ParaLifecycles::get(&c), Some(ParaLifecycle::Parachain));

			assert_eq!(Paras::current_code(&a), Some(vec![2].into()));
			assert_eq!(Paras::current_code(&b), Some(vec![1].into()));
			assert_eq!(Paras::current_code(&c), Some(vec![3].into()));
		})
	}

	#[test]
	fn code_hash_at_returns_up_to_end_of_code_retention_period() {
		let code_retention_period = 10;
		let validation_upgrade_delay = 2;

		let paras = vec![(
			0u32.into(),
			ParaGenesisArgs {
				parachain: true,
				genesis_head: dummy_head_data(),
				validation_code: vec![1, 2, 3].into(),
			},
		)];

		let genesis_config = MockGenesisConfig {
			paras: GenesisConfig { paras, ..Default::default() },
			configuration: crate::configuration::GenesisConfig {
				config: HostConfiguration {
					code_retention_period,
					validation_upgrade_delay,
					pvf_checking_enabled: false,
					..Default::default()
				},
				..Default::default()
			},
			..Default::default()
		};

		new_test_ext(genesis_config).execute_with(|| {
			let para_id = ParaId::from(0);
			let old_code: ValidationCode = vec![1, 2, 3].into();
			let new_code: ValidationCode = vec![4, 5, 6].into();
			Paras::schedule_code_upgrade(para_id, new_code.clone(), 0, &Configuration::config());

			// The new validation code can be applied but a new parablock hasn't gotten in yet,
			// so the old code should still be current.
			run_to_block(3, None);
			assert_eq!(Paras::current_code(&para_id), Some(old_code.clone()));

			run_to_block(10, None);
			Paras::note_new_head(para_id, Default::default(), 7);

			assert_eq!(Paras::past_code_meta(&para_id).upgrade_times, vec![upgrade_at(2, 10)]);
			assert_eq!(Paras::current_code(&para_id), Some(new_code.clone()));

			// Make sure that the old code is available **before** the code retion period passes.
			run_to_block(10 + code_retention_period, None);
			assert_eq!(Paras::code_by_hash(&old_code.hash()), Some(old_code.clone()));
			assert_eq!(Paras::code_by_hash(&new_code.hash()), Some(new_code.clone()));

			run_to_block(10 + code_retention_period + 1, None);

			// code entry should be pruned now.

			assert_eq!(
				Paras::past_code_meta(&para_id),
				ParaPastCodeMeta { upgrade_times: Vec::new(), last_pruned: Some(10) },
			);

			assert_eq!(Paras::code_by_hash(&old_code.hash()), None); // pruned :(
			assert_eq!(Paras::code_by_hash(&new_code.hash()), Some(new_code.clone()));
		});
	}

	#[test]
	fn code_ref_is_cleaned_correctly() {
		new_test_ext(Default::default()).execute_with(|| {
			let code: ValidationCode = vec![1, 2, 3].into();
			Paras::increase_code_ref(&code.hash(), &code);
			Paras::increase_code_ref(&code.hash(), &code);

			assert!(<Paras as Store>::CodeByHash::contains_key(code.hash()));
			assert_eq!(<Paras as Store>::CodeByHashRefs::get(code.hash()), 2);

			Paras::decrease_code_ref(&code.hash());

			assert!(<Paras as Store>::CodeByHash::contains_key(code.hash()));
			assert_eq!(<Paras as Store>::CodeByHashRefs::get(code.hash()), 1);

			Paras::decrease_code_ref(&code.hash());

			assert!(!<Paras as Store>::CodeByHash::contains_key(code.hash()));
			assert!(!<Paras as Store>::CodeByHashRefs::contains_key(code.hash()));
		});
	}

	#[test]
	fn pvf_check_coalescing_onboarding_and_upgrade() {
		let validation_upgrade_delay = 5;

		let a = ParaId::from(111);
		let b = ParaId::from(222);
		let validation_code: ValidationCode = vec![3, 2, 1].into();

		let paras = vec![(
			a,
			ParaGenesisArgs {
				parachain: true,
				genesis_head: Default::default(),
				validation_code: ValidationCode(vec![]), // valid since in genesis
			},
		)];

		let genesis_config = MockGenesisConfig {
			paras: GenesisConfig { paras, ..Default::default() },
			configuration: crate::configuration::GenesisConfig {
				config: HostConfiguration {
					pvf_checking_enabled: true,
					validation_upgrade_delay,
					..Default::default()
				},
				..Default::default()
			},
			..Default::default()
		};

		new_test_ext(genesis_config).execute_with(|| {
			// At this point `a` is already onboarded. Run to block 1 performing session change at
			// the end of block #0.
			run_to_block(2, Some(vec![1]));

			// Expected current session index.
			const EXPECTED_SESSION: SessionIndex = 1;
			// Relay parent of the parablock that schedules the upgrade.
			const RELAY_PARENT: BlockNumber = 1;

			// Now we register `b` with `validation_code`
			assert_ok!(Paras::schedule_para_initialize(
				b,
				ParaGenesisArgs {
					parachain: true,
					genesis_head: vec![2].into(),
					validation_code: validation_code.clone(),
				},
			));

			// And now at the same time upgrade `a` to `validation_code`
			Paras::schedule_code_upgrade(
				a,
				validation_code.clone(),
				RELAY_PARENT,
				&Configuration::config(),
			);
			assert!(!Paras::pvfs_require_precheck().is_empty());

			// Supermajority of validators vote for `validation_code`. It should be approved.
			IntoIterator::into_iter([0, 1, 2, 3])
				.map(|i| PvfCheckStatement {
					accept: true,
					subject: validation_code.hash(),
					session_index: EXPECTED_SESSION,
					validator_index: i.into(),
				})
				.for_each(sign_and_include_pvf_check_statement);

			// Check that `b` actually onboards.
			assert_eq!(<Paras as Store>::ActionsQueue::get(EXPECTED_SESSION + 2), vec![b]);

			// Check that the upgrade got scheduled.
			assert_eq!(
				<Paras as Store>::FutureCodeUpgrades::get(&a),
				Some(RELAY_PARENT + validation_upgrade_delay),
			);
		});
	}

	#[test]
	fn pvf_check_onboarding_reject_on_expiry() {
		let pvf_voting_ttl = 2;
		let a = ParaId::from(111);
		let validation_code: ValidationCode = vec![3, 2, 1].into();

		let genesis_config = MockGenesisConfig {
			configuration: crate::configuration::GenesisConfig {
				config: HostConfiguration {
					pvf_checking_enabled: true,
					pvf_voting_ttl,
					..Default::default()
				},
				..Default::default()
			},
			..Default::default()
		};

		new_test_ext(genesis_config).execute_with(|| {
			run_to_block(1, Some(vec![1]));

			assert_ok!(Paras::schedule_para_initialize(
				a,
				ParaGenesisArgs {
					parachain: false,
					genesis_head: vec![2].into(),
					validation_code: validation_code.clone(),
				},
			));

			// Make sure that we kicked off the PVF vote for this validation code and that the
			// validation code is stored.
			assert!(<Paras as Store>::PvfActiveVoteMap::get(&validation_code.hash()).is_some());
			check_code_is_stored(&validation_code);

			// Skip 2 sessions (i.e. `pvf_voting_ttl`) verifying that the code is still stored in
			// the intermediate session.
			assert_eq!(pvf_voting_ttl, 2);
			run_to_block(2, Some(vec![2]));
			check_code_is_stored(&validation_code);
			run_to_block(3, Some(vec![3]));

			// --- At this point the PVF vote for onboarding should be rejected.

			// Verify that the PVF is no longer stored and there is no active PVF vote.
			check_code_is_not_stored(&validation_code);
			assert!(<Paras as Store>::PvfActiveVoteMap::get(&validation_code.hash()).is_none());
			assert!(Paras::pvfs_require_precheck().is_empty());

			// Verify that at this point we can again try to initialize the same para.
			assert!(Paras::can_schedule_para_initialize(&a));
		});
	}

	#[test]
	fn pvf_check_upgrade_reject() {
		let a = ParaId::from(111);
		let new_code: ValidationCode = vec![3, 2, 1].into();

		let paras = vec![(
			a,
			ParaGenesisArgs {
				parachain: false,
				genesis_head: Default::default(),
				validation_code: ValidationCode(vec![]), // valid since in genesis
			},
		)];

		let genesis_config = MockGenesisConfig {
			paras: GenesisConfig { paras, ..Default::default() },
			configuration: crate::configuration::GenesisConfig {
				config: HostConfiguration { pvf_checking_enabled: true, ..Default::default() },
				..Default::default()
			},
			..Default::default()
		};

		new_test_ext(genesis_config).execute_with(|| {
			// At this point `a` is already onboarded. Run to block 1 performing session change at
			// the end of block #0.
			run_to_block(2, Some(vec![1]));

			// Relay parent of the block that schedules the upgrade.
			const RELAY_PARENT: BlockNumber = 1;
			// Expected current session index.
			const EXPECTED_SESSION: SessionIndex = 1;

			Paras::schedule_code_upgrade(
				a,
				new_code.clone(),
				RELAY_PARENT,
				&Configuration::config(),
			);
			check_code_is_stored(&new_code);

			// Supermajority of validators vote against `new_code`. PVF should be rejected.
			IntoIterator::into_iter([0, 1, 2, 3])
				.map(|i| PvfCheckStatement {
					accept: false,
					subject: new_code.hash(),
					session_index: EXPECTED_SESSION,
					validator_index: i.into(),
				})
				.for_each(sign_and_include_pvf_check_statement);

			// Verify that the new code is discarded.
			check_code_is_not_stored(&new_code);

			assert!(<Paras as Store>::PvfActiveVoteMap::get(&new_code.hash()).is_none());
			assert!(Paras::pvfs_require_precheck().is_empty());
			assert!(<Paras as Store>::FutureCodeHash::get(&a).is_none());
		});
	}

	#[test]
	fn pvf_check_submit_vote() {
		let code_a: ValidationCode = vec![3, 2, 1].into();
		let code_b: ValidationCode = vec![1, 2, 3].into();

		let check = |stmt: PvfCheckStatement| -> (Result<_, _>, Result<_, _>) {
			let validators = &[
				Sr25519Keyring::Alice,
				Sr25519Keyring::Bob,
				Sr25519Keyring::Charlie,
				Sr25519Keyring::Dave,
				Sr25519Keyring::Ferdie,
				Sr25519Keyring::Eve, // <- this validator is not in the set
			];
			let signature: ValidatorSignature =
				validators[stmt.validator_index.0 as usize].sign(&stmt.signing_payload()).into();

			let call = Call::include_pvf_check_statement {
				stmt: stmt.clone(),
				signature: signature.clone(),
			};
			let validate_unsigned =
				<Paras as ValidateUnsigned>::validate_unsigned(TransactionSource::InBlock, &call)
					.map(|_| ());
			let dispatch_result =
				Paras::include_pvf_check_statement(None.into(), stmt.clone(), signature.clone());

			(validate_unsigned, dispatch_result)
		};

		let genesis_config = MockGenesisConfig {
			configuration: crate::configuration::GenesisConfig {
				config: HostConfiguration { pvf_checking_enabled: true, ..Default::default() },
				..Default::default()
			},
			..Default::default()
		};

		new_test_ext(genesis_config).execute_with(|| {
			// Important to run this to seed the validators.
			run_to_block(1, Some(vec![1]));

			assert_ok!(Paras::schedule_para_initialize(
				1000.into(),
				ParaGenesisArgs {
					parachain: false,
					genesis_head: vec![2].into(),
					validation_code: code_a.clone(),
				},
			));

			assert_eq!(
				check(PvfCheckStatement {
					accept: false,
					subject: code_a.hash(),
					session_index: 1,
					validator_index: 1.into(),
				}),
				(Ok(()), Ok(())),
			);

			// A vote in the same direction.
			let (unsigned, dispatch) = check(PvfCheckStatement {
				accept: false,
				subject: code_a.hash(),
				session_index: 1,
				validator_index: 1.into(),
			});
			assert_eq!(unsigned, Err(InvalidTransaction::Custom(INVALID_TX_DOUBLE_VOTE).into()));
			assert_err!(dispatch, Error::<Test>::PvfCheckDoubleVote);

			// Equivocation
			let (unsigned, dispatch) = check(PvfCheckStatement {
				accept: true,
				subject: code_a.hash(),
				session_index: 1,
				validator_index: 1.into(),
			});
			assert_eq!(unsigned, Err(InvalidTransaction::Custom(INVALID_TX_DOUBLE_VOTE).into()));
			assert_err!(dispatch, Error::<Test>::PvfCheckDoubleVote);

			// Vote for an earlier session.
			let (unsigned, dispatch) = check(PvfCheckStatement {
				accept: false,
				subject: code_a.hash(),
				session_index: 0,
				validator_index: 1.into(),
			});
			assert_eq!(unsigned, Err(InvalidTransaction::Stale.into()));
			assert_err!(dispatch, Error::<Test>::PvfCheckStatementStale);

			// Vote for an later session.
			let (unsigned, dispatch) = check(PvfCheckStatement {
				accept: false,
				subject: code_a.hash(),
				session_index: 2,
				validator_index: 1.into(),
			});
			assert_eq!(unsigned, Err(InvalidTransaction::Future.into()));
			assert_err!(dispatch, Error::<Test>::PvfCheckStatementFuture);

			// Validator not in the set.
			let (unsigned, dispatch) = check(PvfCheckStatement {
				accept: false,
				subject: code_a.hash(),
				session_index: 1,
				validator_index: 5.into(),
			});
			assert_eq!(
				unsigned,
				Err(InvalidTransaction::Custom(INVALID_TX_BAD_VALIDATOR_IDX).into())
			);
			assert_err!(dispatch, Error::<Test>::PvfCheckValidatorIndexOutOfBounds);

			// Bad subject (code_b)
			let (unsigned, dispatch) = check(PvfCheckStatement {
				accept: false,
				subject: code_b.hash(),
				session_index: 1,
				validator_index: 1.into(),
			});
			assert_eq!(unsigned, Err(InvalidTransaction::Custom(INVALID_TX_BAD_SUBJECT).into()));
			assert_err!(dispatch, Error::<Test>::PvfCheckSubjectInvalid);
		});
	}

	#[test]
	fn verify_upgrade_go_ahead_signal_is_externally_accessible() {
		use primitives::v1::well_known_keys;

		let a = ParaId::from(2020);

		new_test_ext(Default::default()).execute_with(|| {
			assert!(sp_io::storage::get(&well_known_keys::upgrade_go_ahead_signal(a)).is_none());
			<Paras as Store>::UpgradeGoAheadSignal::insert(&a, UpgradeGoAhead::GoAhead);
			assert_eq!(
				sp_io::storage::get(&well_known_keys::upgrade_go_ahead_signal(a)).unwrap(),
				vec![1u8],
			);
		});
	}

	#[test]
	fn verify_upgrade_restriction_signal_is_externally_accessible() {
		use primitives::v1::well_known_keys;

		let a = ParaId::from(2020);