paras.rs

			System::on_finalize(b);

			System::on_initialize(b + 1);
			System::set_block_number(b + 1);

			Shared::initializer_initialize(b + 1);
			Paras::initializer_initialize(b + 1);
		}
	}

	fn upgrade_at(expected_at: BlockNumber, activated_at: BlockNumber) -> ReplacementTimes<BlockNumber> {
		ReplacementTimes { expected_at, activated_at }
	}

	fn check_code_is_stored(validation_code: &ValidationCode) {
		assert!(<Paras as Store>::CodeByHashRefs::get(validation_code.hash()) != 0);
		assert!(<Paras as Store>::CodeByHash::contains_key(validation_code.hash()));
	}

	fn check_code_is_not_stored(validation_code: &ValidationCode) {
		assert!(!<Paras as Store>::CodeByHashRefs::contains_key(validation_code.hash()));
		assert!(!<Paras as Store>::CodeByHash::contains_key(validation_code.hash()));
	}

	#[test]
	fn para_past_code_meta_gives_right_code() {
		let mut past_code = ParaPastCodeMeta::default();
		assert_eq!(past_code.code_at(0u32), Some(UseCodeAt::Current));

		past_code.note_replacement(10, 12);
		assert_eq!(past_code.code_at(0), Some(UseCodeAt::ReplacedAt(10)));
		assert_eq!(past_code.code_at(10), Some(UseCodeAt::ReplacedAt(10)));
		assert_eq!(past_code.code_at(11), Some(UseCodeAt::ReplacedAt(10)));
		assert_eq!(past_code.code_at(12), Some(UseCodeAt::Current));

		past_code.note_replacement(20, 25);
		assert_eq!(past_code.code_at(1), Some(UseCodeAt::ReplacedAt(10)));
		assert_eq!(past_code.code_at(10), Some(UseCodeAt::ReplacedAt(10)));
		assert_eq!(past_code.code_at(11), Some(UseCodeAt::ReplacedAt(10)));
		assert_eq!(past_code.code_at(12), Some(UseCodeAt::ReplacedAt(20)));
		assert_eq!(past_code.code_at(24), Some(UseCodeAt::ReplacedAt(20)));
		assert_eq!(past_code.code_at(25), Some(UseCodeAt::Current));

		past_code.note_replacement(30, 30);
		assert_eq!(past_code.code_at(1), Some(UseCodeAt::ReplacedAt(10)));
		assert_eq!(past_code.code_at(10), Some(UseCodeAt::ReplacedAt(10)));
		assert_eq!(past_code.code_at(11), Some(UseCodeAt::ReplacedAt(10)));
		assert_eq!(past_code.code_at(12), Some(UseCodeAt::ReplacedAt(20)));
		assert_eq!(past_code.code_at(24), Some(UseCodeAt::ReplacedAt(20)));
		assert_eq!(past_code.code_at(25), Some(UseCodeAt::ReplacedAt(30)));
		assert_eq!(past_code.code_at(30), Some(UseCodeAt::Current));

		past_code.last_pruned = Some(5);
		assert_eq!(past_code.code_at(1), None);
		assert_eq!(past_code.code_at(5), None);
		assert_eq!(past_code.code_at(6), Some(UseCodeAt::ReplacedAt(10)));
		assert_eq!(past_code.code_at(24), Some(UseCodeAt::ReplacedAt(20)));
		assert_eq!(past_code.code_at(25), Some(UseCodeAt::ReplacedAt(30)));
		assert_eq!(past_code.code_at(30), Some(UseCodeAt::Current));

	}

	#[test]
	fn para_past_code_pruning_works_correctly() {
		let mut past_code = ParaPastCodeMeta::default();
		past_code.note_replacement(10u32, 10);
		past_code.note_replacement(20, 25);
		past_code.note_replacement(30, 35);

		let old = past_code.clone();
		assert!(past_code.prune_up_to(9).collect::<Vec<_>>().is_empty());
		assert_eq!(old, past_code);

		assert_eq!(past_code.prune_up_to(10).collect::<Vec<_>>(), vec![10]);
		assert_eq!(past_code, ParaPastCodeMeta {
			upgrade_times: vec![upgrade_at(20, 25), upgrade_at(30, 35)],
			last_pruned: Some(10),
		});

		assert!(past_code.prune_up_to(21).collect::<Vec<_>>().is_empty());

		assert_eq!(past_code.prune_up_to(26).collect::<Vec<_>>(), vec![20]);
		assert_eq!(past_code, ParaPastCodeMeta {
			upgrade_times: vec![upgrade_at(30, 35)],
			last_pruned: Some(25),
		});

		past_code.note_replacement(40, 42);
		past_code.note_replacement(50, 53);
		past_code.note_replacement(60, 66);

		assert_eq!(past_code, ParaPastCodeMeta {
			upgrade_times: vec![upgrade_at(30, 35), upgrade_at(40, 42), upgrade_at(50, 53), upgrade_at(60, 66)],
			last_pruned: Some(25),
		});

		assert_eq!(past_code.prune_up_to(60).collect::<Vec<_>>(), vec![30, 40, 50]);
		assert_eq!(past_code, ParaPastCodeMeta {
			upgrade_times: vec![upgrade_at(60, 66)],
			last_pruned: Some(53),
		});

		assert_eq!(past_code.most_recent_change(), Some(60));
		assert_eq!(past_code.prune_up_to(66).collect::<Vec<_>>(), vec![60]);

		assert_eq!(past_code, ParaPastCodeMeta {
			upgrade_times: Vec::new(),
			last_pruned: Some(66),
		});
	}

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

		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 = ParaId::from(0u32);
			let at_block: BlockNumber = 10;
			let included_block: BlockNumber = 12;
			let validation_code = ValidationCode(vec![1, 2, 3]);

			Paras::increase_code_ref(&validation_code.hash(), &validation_code);
			<Paras as Store>::PastCodeHash::insert(&(id, at_block), &validation_code.hash());
			<Paras as Store>::PastCodePruning::put(&vec![(id, included_block)]);

			{
				let mut code_meta = Paras::past_code_meta(&id);
				code_meta.note_replacement(at_block, included_block);
				<Paras as Store>::PastCodeMeta::insert(&id, &code_meta);
			}

			let pruned_at: BlockNumber = included_block + code_retention_period + 1;
			assert_eq!(<Paras as Store>::PastCodeHash::get(&(id, at_block)), Some(validation_code.hash()));
			check_code_is_stored(&validation_code);

			run_to_block(pruned_at - 1, None);
			assert_eq!(<Paras as Store>::PastCodeHash::get(&(id, at_block)), Some(validation_code.hash()));
			assert_eq!(Paras::past_code_meta(&id).most_recent_change(), Some(at_block));
			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: Default::default(),
				validation_code: Default::default(),
			}),
		];

		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(Default::default()));

			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: Default::default(),
				validation_code: Default::default(),
			}),
			(1u32.into(), ParaGenesisArgs {
				parachain: false,
				genesis_head: Default::default(),
				validation_code: Default::default(),
			}),
		];

		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 original_code = ValidationCode(vec![1, 2, 3]);
		let paras = vec![
			(0u32.into(), ParaGenesisArgs {
				parachain: true,
				genesis_head: Default::default(),
				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,
					..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;
				Paras::schedule_code_upgrade(para_id, new_code.clone(), expected_at);
				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
			};

			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::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_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 original_code = ValidationCode(vec![1, 2, 3]);
		let paras = vec![
			(0u32.into(), ParaGenesisArgs {
				parachain: true,
				genesis_head: Default::default(),
				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,
					..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;
				Paras::schedule_code_upgrade(para_id, new_code.clone(), expected_at);
				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()));

				expected_at
			};

			run_to_block(expected_at + 1 + 4, None);

			// the candidate is in the context of the first descendent of `expected_at`, and triggers
			// the upgrade.
			{
				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),
				);

				// Some hypothetical block which would have triggered the code change
				// should still use the old code.
				assert_eq!(
					Paras::past_code_meta(&para_id).code_at(expected_at),
					Some(UseCodeAt::ReplacedAt(expected_at)),
				);

				// Some hypothetical block at the context which actually triggered the
				// code change should still use the old code.
				assert_eq!(
					Paras::past_code_meta(&para_id).code_at(expected_at + 4),
					Some(UseCodeAt::ReplacedAt(expected_at)),
				);

				// Some hypothetical block at the context after the code was upgraded
				// should use the new code.
				assert_eq!(
					Paras::past_code_meta(&para_id).code_at(expected_at + 4 + 1),
					Some(UseCodeAt::Current),
				);

				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_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 paras = vec![
			(0u32.into(), ParaGenesisArgs {
				parachain: true,
				genesis_head: Default::default(),
				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,
					..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(), 8);
			assert_eq!(<Paras as Store>::FutureCodeUpgrades::get(&para_id), Some(8));
			assert_eq!(<Paras as Store>::FutureCodeHash::get(&para_id), Some(new_code.hash()));
			check_code_is_stored(&new_code);

			Paras::schedule_code_upgrade(para_id, newer_code.clone(), 10);
			assert_eq!(<Paras as Store>::FutureCodeUpgrades::get(&para_id), Some(8));
			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 = 10;

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

		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(|| {
			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 + 5;
				Paras::schedule_code_upgrade(para_id, new_code.clone(), expected_at);
				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
			};

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

			// Just scheduling cleanup shouldn't change anything.
			{
				assert_eq!(
					<Paras as Store>::ActionsQueue::get(Paras::scheduled_session()),
					vec![para_id],
				);
				assert_eq!(Paras::parachains(), vec![para_id]);

				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);

				assert_eq!(<Paras as Store>::Heads::get(&para_id), Some(Default::default()));
			}

			// run to block #4, with a 2 session changes at the end of the block 2 & 3.
			run_to_block(4, Some(vec![3,4]));

			// cleaning up the parachain should place the current parachain code
			// into the past code buffer & schedule cleanup.
			assert_eq!(Paras::past_code_meta(&para_id).most_recent_change(), Some(3));
			assert_eq!(<Paras as Store>::PastCodeHash::get(&(para_id, 3)), Some(original_code.hash()));
			assert_eq!(<Paras as Store>::PastCodePruning::get(), vec![(para_id, 3)]);
			check_code_is_stored(&original_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());
			check_code_is_not_stored(&new_code);

			// run to do the final cleanup
			let cleaned_up_at = 3 + 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, 3)).is_none());
			assert!(<Paras as Store>::PastCodePruning::get().is_empty());
			check_code_is_not_stored(&original_code);
		});
	}

	#[test]
	fn para_incoming_at_session() {
		new_test_ext(Default::default()).execute_with(|| {
			run_to_block(1, None);

			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: vec![1].into(),
				},
			));

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

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

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

			// Lifecycle is tracked correctly
			assert_eq!(ParaLifecycles::get(&a), Some(ParaLifecycle::Onboarding));
			assert_eq!(ParaLifecycles::get(&b), Some(ParaLifecycle::Onboarding));
			assert_eq!(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!(ParaLifecycles::get(&a), Some(ParaLifecycle::Onboarding));
			assert_eq!(ParaLifecycles::get(&b), Some(ParaLifecycle::Onboarding));
			assert_eq!(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!(ParaLifecycles::get(&a), Some(ParaLifecycle::Parathread));
			assert_eq!(ParaLifecycles::get(&b), Some(ParaLifecycle::Parachain));
			assert_eq!(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_at_with_intermediate() {
		let code_retention_period = 10;

		let paras = vec![
			(0u32.into(), ParaGenesisArgs {
				parachain: true,
				genesis_head: Default::default(),
				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,
					..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(), 10);

			// no intermediate, falls back on current/past.
			assert_eq!(Paras::validation_code_at(para_id, 1, None), Some(old_code.clone()));
			assert_eq!(Paras::validation_code_at(para_id, 10, None), Some(old_code.clone()));
			assert_eq!(Paras::validation_code_at(para_id, 100, None), Some(old_code.clone()));

			// intermediate before upgrade meant to be applied, falls back on current.
			assert_eq!(Paras::validation_code_at(para_id, 9, Some(8)), Some(old_code.clone()));
			assert_eq!(Paras::validation_code_at(para_id, 10, Some(9)), Some(old_code.clone()));
			assert_eq!(Paras::validation_code_at(para_id, 11, Some(9)), Some(old_code.clone()));

			// intermediate at or after upgrade applied
			assert_eq!(Paras::validation_code_at(para_id, 11, Some(10)), Some(new_code.clone()));
			assert_eq!(Paras::validation_code_at(para_id, 100, Some(11)), Some(new_code.clone()));

			run_to_block(code_retention_period + 5, None);

			// at <= intermediate not allowed
			assert_eq!(Paras::validation_code_at(para_id, 10, Some(10)), None);
			assert_eq!(Paras::validation_code_at(para_id, 9, Some(10)), None);
		});
	}

	#[test]
	fn code_at_returns_up_to_end_of_code_retention_period() {
		let code_retention_period = 10;

		let paras = vec![
			(0u32.into(), ParaGenesisArgs {
				parachain: true,
				genesis_head: Default::default(),
				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,
					..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(), 2);

			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::validation_code_at(para_id, 2, None), Some(old_code.clone()));
			assert_eq!(Paras::validation_code_at(para_id, 3, None), Some(old_code.clone()));
			assert_eq!(Paras::validation_code_at(para_id, 9, None), Some(old_code.clone()));
			assert_eq!(Paras::validation_code_at(para_id, 10, None), Some(new_code.clone()));

			run_to_block(10 + code_retention_period, None);

			assert_eq!(Paras::validation_code_at(para_id, 2, None), Some(old_code.clone()));
			assert_eq!(Paras::validation_code_at(para_id, 3, None), Some(old_code.clone()));
			assert_eq!(Paras::validation_code_at(para_id, 9, None), Some(old_code.clone()));
			assert_eq!(Paras::validation_code_at(para_id, 10, None), 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::validation_code_at(para_id, 2, None), None); // pruned :(
			assert_eq!(Paras::validation_code_at(para_id, 9, None), None);
			assert_eq!(Paras::validation_code_at(para_id, 10, None), Some(new_code.clone()));
			assert_eq!(Paras::validation_code_at(para_id, 11, None), 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!(CodeByHash::contains_key(code.hash()));
			assert_eq!(CodeByHashRefs::get(code.hash()), 2);

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

			assert!(CodeByHash::contains_key(code.hash()));
			assert_eq!(CodeByHashRefs::get(code.hash()), 1);

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

			assert!(!CodeByHash::contains_key(code.hash()));
			assert!(!CodeByHashRefs::contains_key(code.hash()));
		});
	}
}