tests.rs

// Copyright 2020 Parity Technologies (UK) Ltd.
// This file is part of Polkadot.

// Polkadot is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Polkadot is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.

use super::*;
use assert_matches::assert_matches;
use polkadot_erasure_coding::{branches, obtain_chunks_v1 as obtain_chunks};
use polkadot_node_network_protocol::ObservedRole;
use polkadot_node_subsystem_util::TimeoutExt;
use polkadot_primitives::v1::{
	AvailableData, BlockData, CandidateCommitments, CandidateDescriptor, GroupIndex,
	GroupRotationInfo, HeadData, OccupiedCore, PersistedValidationData, PoV, ScheduledCore,
};
use polkadot_subsystem_testhelpers::{self as test_helpers};

use futures::{executor, future, Future};
use futures_timer::Delay;
use sc_keystore::LocalKeystore;
use smallvec::smallvec;
use sp_application_crypto::AppKey;
use sp_keystore::{SyncCryptoStore, SyncCryptoStorePtr};
use std::{sync::Arc, time::Duration};

macro_rules! view {
		( $( $hash:expr ),* $(,)? ) => [
			View(vec![ $( $hash.clone() ),* ])
		];
	}

macro_rules! delay {
	($delay:expr) => {
		Delay::new(Duration::from_millis($delay)).await;
	};
}

fn chunk_protocol_message(
	message: AvailabilityGossipMessage,
) -> protocol_v1::AvailabilityDistributionMessage {
	protocol_v1::AvailabilityDistributionMessage::Chunk(
		message.candidate_hash,
		message.erasure_chunk,
	)
}

struct TestHarness {
	virtual_overseer: test_helpers::TestSubsystemContextHandle<AvailabilityDistributionMessage>,
}

fn test_harness<T: Future<Output = ()>>(
	keystore: SyncCryptoStorePtr,
	test: impl FnOnce(TestHarness) -> T,
) {
	let _ = env_logger::builder()
		.is_test(true)
		.filter(
			Some("polkadot_availability_distribution"),
			log::LevelFilter::Trace,
		)
		.try_init();

	let pool = sp_core::testing::TaskExecutor::new();

	let (context, virtual_overseer) = test_helpers::make_subsystem_context(pool.clone());

	let subsystem = AvailabilityDistributionSubsystem::new(keystore, Default::default());
	let subsystem = subsystem.run(context);

	let test_fut = test(TestHarness { virtual_overseer });

	futures::pin_mut!(test_fut);
	futures::pin_mut!(subsystem);

	executor::block_on(future::select(test_fut, subsystem));
}

const TIMEOUT: Duration = Duration::from_millis(100);

async fn overseer_signal(
	overseer: &mut test_helpers::TestSubsystemContextHandle<AvailabilityDistributionMessage>,
	signal: OverseerSignal,
) {
	delay!(50);
	overseer
		.send(FromOverseer::Signal(signal))
		.timeout(TIMEOUT)
		.await
		.expect("10ms is more than enough for sending signals.");
}

async fn overseer_send(
	overseer: &mut test_helpers::TestSubsystemContextHandle<AvailabilityDistributionMessage>,
	msg: AvailabilityDistributionMessage,
) {
	log::trace!("Sending message:\n{:?}", &msg);
	overseer
		.send(FromOverseer::Communication { msg })
		.timeout(TIMEOUT)
		.await
		.expect("10ms is more than enough for sending messages.");
}

async fn overseer_recv(
	overseer: &mut test_helpers::TestSubsystemContextHandle<AvailabilityDistributionMessage>,
) -> AllMessages {
	log::trace!("Waiting for message ...");
	let msg = overseer
		.recv()
		.timeout(TIMEOUT)
		.await
		.expect("TIMEOUT is enough to recv.");
	log::trace!("Received message:\n{:?}", &msg);
	msg
}

fn dummy_occupied_core(para: ParaId) -> CoreState {
	CoreState::Occupied(OccupiedCore {
		para_id: para,
		next_up_on_available: None,
		occupied_since: 0,
		time_out_at: 5,
		next_up_on_time_out: None,
		availability: Default::default(),
		group_responsible: GroupIndex::from(0),
	})
}

use sp_keyring::Sr25519Keyring;

#[derive(Clone)]
struct TestState {
	chain_ids: Vec<ParaId>,
	validators: Vec<Sr25519Keyring>,
	validator_public: Vec<ValidatorId>,
	validator_index: Option<ValidatorIndex>,
	validator_groups: (Vec<Vec<ValidatorIndex>>, GroupRotationInfo),
	head_data: HashMap<ParaId, HeadData>,
	keystore: SyncCryptoStorePtr,
	relay_parent: Hash,
	ancestors: Vec<Hash>,
	availability_cores: Vec<CoreState>,
	persisted_validation_data: PersistedValidationData,
}

fn validator_pubkeys(val_ids: &[Sr25519Keyring]) -> Vec<ValidatorId> {
	val_ids.iter().map(|v| v.public().into()).collect()
}

impl Default for TestState {
	fn default() -> Self {
		let chain_a = ParaId::from(1);
		let chain_b = ParaId::from(2);

		let chain_ids = vec![chain_a, chain_b];

		let validators = vec![
			Sr25519Keyring::Ferdie, // <- this node, role: validator
			Sr25519Keyring::Alice,
			Sr25519Keyring::Bob,
			Sr25519Keyring::Charlie,
			Sr25519Keyring::Dave,
		];

		let keystore: SyncCryptoStorePtr = Arc::new(LocalKeystore::in_memory());

		SyncCryptoStore::sr25519_generate_new(
			&*keystore,
			ValidatorId::ID,
			Some(&validators[0].to_seed()),
		)
		.expect("Insert key into keystore");

		let validator_public = validator_pubkeys(&validators);

		let validator_groups = vec![vec![2, 0, 4], vec![1], vec![3]];
		let group_rotation_info = GroupRotationInfo {
			session_start_block: 0,
			group_rotation_frequency: 100,
			now: 1,
		};
		let validator_groups = (validator_groups, group_rotation_info);

		let availability_cores = vec![
			CoreState::Scheduled(ScheduledCore {
				para_id: chain_ids[0],
				collator: None,
			}),
			CoreState::Scheduled(ScheduledCore {
				para_id: chain_ids[1],
				collator: None,
			}),
		];

		let mut head_data = HashMap::new();
		head_data.insert(chain_a, HeadData(vec![4, 5, 6]));
		head_data.insert(chain_b, HeadData(vec![7, 8, 9]));

		let ancestors = vec![
			Hash::repeat_byte(0x44),
			Hash::repeat_byte(0x33),
			Hash::repeat_byte(0x22),
		];
		let relay_parent = Hash::repeat_byte(0x05);

		let persisted_validation_data = PersistedValidationData {
			parent_head: HeadData(vec![7, 8, 9]),
			block_number: Default::default(),
			hrmp_mqc_heads: Vec::new(),
			dmq_mqc_head: Default::default(),
		};

		let validator_index = Some((validators.len() - 1) as ValidatorIndex);

		Self {
			chain_ids,
			keystore,
			validators,
			validator_public,
			validator_groups,
			availability_cores,
			head_data,
			persisted_validation_data,
			relay_parent,
			ancestors,
			validator_index,
		}
	}
}

fn make_available_data(test: &TestState, pov: PoV) -> AvailableData {
	AvailableData {
		validation_data: test.persisted_validation_data.clone(),
		pov,
	}
}

fn make_erasure_root(test: &TestState, pov: PoV) -> Hash {
	let available_data = make_available_data(test, pov);

	let chunks = obtain_chunks(test.validators.len(), &available_data).unwrap();
	branches(&chunks).root()
}

fn make_valid_availability_gossip(
	test: &TestState,
	candidate_hash: CandidateHash,
	erasure_chunk_index: u32,
	pov: PoV,
) -> AvailabilityGossipMessage {
	let available_data = make_available_data(test, pov);

	let erasure_chunks = derive_erasure_chunks_with_proofs(test.validators.len(), &available_data);

	let erasure_chunk: ErasureChunk = erasure_chunks
		.get(erasure_chunk_index as usize)
		.expect("Must be valid or input is oob")
		.clone();

	AvailabilityGossipMessage {
		candidate_hash,
		erasure_chunk,
	}
}

#[derive(Default)]
struct TestCandidateBuilder {
	para_id: ParaId,
	head_data: HeadData,
	pov_hash: Hash,
	relay_parent: Hash,
	erasure_root: Hash,
}

impl TestCandidateBuilder {
	fn build(self) -> CommittedCandidateReceipt {
		CommittedCandidateReceipt {
			descriptor: CandidateDescriptor {
				para_id: self.para_id,
				pov_hash: self.pov_hash,
				relay_parent: self.relay_parent,
				..Default::default()
			},
			commitments: CandidateCommitments {
				head_data: self.head_data,
				erasure_root: self.erasure_root,
				..Default::default()
			},
		}
	}
}

#[test]
fn helper_integrity() {
	let test_state = TestState::default();

	let pov_block = PoV {
		block_data: BlockData(vec![42, 43, 44]),
	};

	let pov_hash = pov_block.hash();

	let candidate = TestCandidateBuilder {
		para_id: test_state.chain_ids[0],
		relay_parent: test_state.relay_parent,
		pov_hash: pov_hash,
		erasure_root: make_erasure_root(&test_state, pov_block.clone()),
		..Default::default()
	}
	.build();

	let message =
		make_valid_availability_gossip(&test_state, candidate.hash(), 2, pov_block.clone());

	let root = dbg!(&candidate.commitments.erasure_root);

	let anticipated_hash = branch_hash(
		root,
		&message.erasure_chunk.proof,
		dbg!(message.erasure_chunk.index as usize),
	)
	.expect("Must be able to derive branch hash");
	assert_eq!(
		anticipated_hash,
		BlakeTwo256::hash(&message.erasure_chunk.chunk)
	);
}

fn derive_erasure_chunks_with_proofs(
	n_validators: usize,
	available_data: &AvailableData,
) -> Vec<ErasureChunk> {
	let chunks: Vec<Vec<u8>> = obtain_chunks(n_validators, available_data).unwrap();

	// create proofs for each erasure chunk
	let branches = branches(chunks.as_ref());

	let erasure_chunks = branches
		.enumerate()
		.map(|(index, (proof, chunk))| ErasureChunk {
			chunk: chunk.to_vec(),
			index: index as _,
			proof,
		})
		.collect::<Vec<ErasureChunk>>();

	erasure_chunks
}

#[test]
fn reputation_verification() {
	let test_state = TestState::default();

	test_harness(test_state.keystore.clone(), |test_harness| async move {
		let TestHarness {
			mut virtual_overseer,
		} = test_harness;

		let expected_head_data = test_state.head_data.get(&test_state.chain_ids[0]).unwrap();

		let pov_block_a = PoV {
			block_data: BlockData(vec![42, 43, 44]),
		};

		let pov_block_b = PoV {
			block_data: BlockData(vec![45, 46, 47]),
		};

		let pov_block_c = PoV {
			block_data: BlockData(vec![48, 49, 50]),
		};

		let pov_hash_a = pov_block_a.hash();
		let pov_hash_b = pov_block_b.hash();
		let pov_hash_c = pov_block_c.hash();

		let candidates = vec![
			TestCandidateBuilder {
				para_id: test_state.chain_ids[0],
				relay_parent: test_state.relay_parent,
				pov_hash: pov_hash_a,
				erasure_root: make_erasure_root(&test_state, pov_block_a.clone()),
				..Default::default()
			}
			.build(),
			TestCandidateBuilder {
				para_id: test_state.chain_ids[0],
				relay_parent: test_state.relay_parent,
				pov_hash: pov_hash_b,
				erasure_root: make_erasure_root(&test_state, pov_block_b.clone()),
				head_data: expected_head_data.clone(),
				..Default::default()
			}
			.build(),
			TestCandidateBuilder {
				para_id: test_state.chain_ids[1],
				relay_parent: Hash::repeat_byte(0xFA),
				pov_hash: pov_hash_c,
				erasure_root: make_erasure_root(&test_state, pov_block_c.clone()),
				head_data: test_state
					.head_data
					.get(&test_state.chain_ids[1])
					.unwrap()
					.clone(),
				..Default::default()
			}
			.build(),
		];

		let TestState {
			chain_ids,
			keystore: _,
			validators: _,
			validator_public,
			validator_groups,
			availability_cores,
			head_data: _,
			persisted_validation_data: _,
			relay_parent: current,
			ancestors,
			validator_index: _,
		} = test_state.clone();

		let _ = validator_groups;
		let _ = availability_cores;

		let peer_a = PeerId::random();
		let peer_b = PeerId::random();
		assert_ne!(&peer_a, &peer_b);

		log::trace!("peer A: {:?}", peer_a);
		log::trace!("peer B: {:?}", peer_b);

		log::trace!("candidate A: {:?}", candidates[0].hash());
		log::trace!("candidate B: {:?}", candidates[1].hash());

		overseer_signal(
			&mut virtual_overseer,
			OverseerSignal::ActiveLeaves(ActiveLeavesUpdate {
				activated: smallvec![current.clone()],
				deactivated: smallvec![],
			}),
		)
		.await;

		overseer_send(
			&mut virtual_overseer,
			AvailabilityDistributionMessage::NetworkBridgeUpdateV1(
				NetworkBridgeEvent::OurViewChange(view![current,]),
			),
		)
		.await;

		// obtain the validators per relay parent
		assert_matches!(
			overseer_recv(&mut virtual_overseer).await,
			AllMessages::RuntimeApi(RuntimeApiMessage::Request(
				relay_parent,
				RuntimeApiRequest::Validators(tx),
			)) => {
				assert_eq!(relay_parent, current);
				tx.send(Ok(validator_public.clone())).unwrap();
			}
		);

		let genesis = Hash::repeat_byte(0xAA);
		// query of k ancestors, we only provide one
		assert_matches!(
			overseer_recv(&mut virtual_overseer).await,
			AllMessages::ChainApi(ChainApiMessage::Ancestors {
				hash: relay_parent,
				k,
				response_channel: tx,
			}) => {
				assert_eq!(relay_parent, current);
				assert_eq!(k, AvailabilityDistributionSubsystem::K + 1);
				// 0xAA..AA will not be included, since there is no mean to determine
				// its session index
				tx.send(Ok(vec![ancestors[0].clone(), genesis])).unwrap();
			}
		);

		// state query for each of them
		assert_matches!(
			overseer_recv(&mut virtual_overseer).await,
			AllMessages::RuntimeApi(RuntimeApiMessage::Request(
				relay_parent,
				RuntimeApiRequest::SessionIndexForChild(tx)
			)) => {
				assert_eq!(relay_parent, current);
				tx.send(Ok(1 as SessionIndex)).unwrap();
			}
		);

		assert_matches!(
			overseer_recv(&mut virtual_overseer).await,
			AllMessages::RuntimeApi(RuntimeApiMessage::Request(
				relay_parent,
				RuntimeApiRequest::SessionIndexForChild(tx)
			)) => {
				assert_eq!(relay_parent, genesis);
				tx.send(Ok(1 as SessionIndex)).unwrap();
			}
		);

		// subsystem peer id collection
		// which will query the availability cores
		assert_matches!(
			overseer_recv(&mut virtual_overseer).await,
			AllMessages::RuntimeApi(RuntimeApiMessage::Request(
				relay_parent,
				RuntimeApiRequest::AvailabilityCores(tx)
			)) => {
				assert_eq!(relay_parent, ancestors[0]);
				// respond with a set of availability core states
				tx.send(Ok(vec![
					dummy_occupied_core(chain_ids[0]),
					dummy_occupied_core(chain_ids[1])
				])).unwrap();
			}
		);

		// now each of the relay parents in the view (1) will
		assert_matches!(
			overseer_recv(&mut virtual_overseer).await,
			AllMessages::RuntimeApi(RuntimeApiMessage::Request(
				relay_parent,
				RuntimeApiRequest::CandidatePendingAvailability(para, tx)
			)) => {
				assert_eq!(relay_parent, ancestors[0]);
				assert_eq!(para, chain_ids[0]);
				tx.send(Ok(Some(
					candidates[0].clone()
				))).unwrap();
			}
		);

		assert_matches!(
			overseer_recv(&mut virtual_overseer).await,
			AllMessages::RuntimeApi(RuntimeApiMessage::Request(
				relay_parent,
				RuntimeApiRequest::CandidatePendingAvailability(para, tx)
			)) => {
				assert_eq!(relay_parent, ancestors[0]);
				assert_eq!(para, chain_ids[1]);
				tx.send(Ok(Some(
					candidates[1].clone()
				))).unwrap();
			}
		);

		for _ in 0usize..1 {
			assert_matches!(
				overseer_recv(&mut virtual_overseer).await,
				AllMessages::RuntimeApi(RuntimeApiMessage::Request(
					_relay_parent,
					RuntimeApiRequest::AvailabilityCores(tx),
				)) => {
					tx.send(Ok(vec![
						CoreState::Occupied(OccupiedCore {
							para_id: chain_ids[0].clone(),
							next_up_on_available: None,
							occupied_since: 0,
							time_out_at: 10,
							next_up_on_time_out: None,
							availability: Default::default(),
							group_responsible: GroupIndex::from(0),
						}),
						CoreState::Free,
						CoreState::Free,
						CoreState::Occupied(OccupiedCore {
							para_id: chain_ids[1].clone(),
							next_up_on_available: None,
							occupied_since: 1,
							time_out_at: 7,
							next_up_on_time_out: None,
							availability: Default::default(),
							group_responsible: GroupIndex::from(0),
						}),
						CoreState::Free,
						CoreState::Free,
					])).unwrap();
				}
			);

			// query the availability cores for each of the paras (2)
			assert_matches!(
				overseer_recv(&mut virtual_overseer).await,
				AllMessages::RuntimeApi(
					RuntimeApiMessage::Request(
						_relay_parent,
						RuntimeApiRequest::CandidatePendingAvailability(para, tx),
					)
				) => {
					assert_eq!(para, chain_ids[0]);
					tx.send(Ok(Some(
						candidates[0].clone()
					))).unwrap();
				}
			);

			assert_matches!(
				overseer_recv(&mut virtual_overseer).await,
				AllMessages::RuntimeApi(RuntimeApiMessage::Request(
					_relay_parent,
					RuntimeApiRequest::CandidatePendingAvailability(para, tx),
				)) => {
					assert_eq!(para, chain_ids[1]);
					tx.send(Ok(Some(
						candidates[1].clone()
					))).unwrap();
				}
			);
		}

		let mut candidates2 = candidates.clone();
		// check if the availability store can provide the desired erasure chunks
		for i in 0usize..2 {
			log::trace!("0000");
			let avail_data = make_available_data(&test_state, pov_block_a.clone());
			let chunks =
				derive_erasure_chunks_with_proofs(test_state.validators.len(), &avail_data);

			let expected;
			// store the chunk to the av store
			assert_matches!(
				overseer_recv(&mut virtual_overseer).await,
				AllMessages::AvailabilityStore(
					AvailabilityStoreMessage::QueryDataAvailability(
						candidate_hash,
						tx,
					)
				) => {
					let index = candidates2.iter().enumerate().find(|x| { x.1.hash() == candidate_hash }).map(|x| x.0).unwrap();
					expected = dbg!(candidates2.swap_remove(index).hash());
					tx.send(
						i == 0
					).unwrap();
				}
			);

			assert_eq!(chunks.len(), test_state.validators.len());

			log::trace!("xxxx");
			// retrieve a stored chunk
			for (j, chunk) in chunks.into_iter().enumerate() {
				log::trace!("yyyy i={}, j={}", i, j);
				if i != 0 {
					// not a validator, so this never happens
					break;
				}
				assert_matches!(
					overseer_recv(&mut virtual_overseer).await,
					AllMessages::AvailabilityStore(
						AvailabilityStoreMessage::QueryChunk(
							candidate_hash,
							idx,
							tx,
						)
					) => {
						assert_eq!(candidate_hash, expected);
						assert_eq!(j as u32, chunk.index);
						assert_eq!(idx, j as u32);
						tx.send(
							Some(chunk.clone())
						).unwrap();
					}
				);
			}
		}
		// setup peer a with interest in current
		overseer_send(
			&mut virtual_overseer,
			AvailabilityDistributionMessage::NetworkBridgeUpdateV1(
				NetworkBridgeEvent::PeerConnected(peer_a.clone(), ObservedRole::Full),
			),
		)
		.await;

		overseer_send(
			&mut virtual_overseer,
			AvailabilityDistributionMessage::NetworkBridgeUpdateV1(
				NetworkBridgeEvent::PeerViewChange(peer_a.clone(), view![current]),
			),
		)
		.await;

		// setup peer b with interest in ancestor
		overseer_send(
			&mut virtual_overseer,
			AvailabilityDistributionMessage::NetworkBridgeUpdateV1(
				NetworkBridgeEvent::PeerConnected(peer_b.clone(), ObservedRole::Full),
			),
		)
		.await;

		overseer_send(
			&mut virtual_overseer,
			AvailabilityDistributionMessage::NetworkBridgeUpdateV1(
				NetworkBridgeEvent::PeerViewChange(peer_b.clone(), view![ancestors[0]]),
			),
		)
		.await;

		delay!(100);

		let valid: AvailabilityGossipMessage = make_valid_availability_gossip(
			&test_state,
			candidates[0].hash(),
			2,
			pov_block_a.clone(),
		);

		{
			// valid (first, from b)
			overseer_send(
				&mut virtual_overseer,
				AvailabilityDistributionMessage::NetworkBridgeUpdateV1(
					NetworkBridgeEvent::PeerMessage(
						peer_b.clone(),
						chunk_protocol_message(valid.clone()),
					),
				),
			)
			.await;

			assert_matches!(
				overseer_recv(&mut virtual_overseer).await,
				AllMessages::NetworkBridge(
					NetworkBridgeMessage::ReportPeer(
						peer,
						rep
					)
				) => {
					assert_eq!(peer, peer_b);
					assert_eq!(rep, BENEFIT_VALID_MESSAGE_FIRST);
				}
			);
		}

		{
			// valid (duplicate, from b)
			overseer_send(
				&mut virtual_overseer,
				AvailabilityDistributionMessage::NetworkBridgeUpdateV1(
					NetworkBridgeEvent::PeerMessage(
						peer_b.clone(),
						chunk_protocol_message(valid.clone()),
					),
				),
			)
			.await;

			assert_matches!(
				overseer_recv(&mut virtual_overseer).await,
				AllMessages::NetworkBridge(
					NetworkBridgeMessage::ReportPeer(
						peer,
						rep
					)
				) => {
					assert_eq!(peer, peer_b);
					assert_eq!(rep, COST_PEER_DUPLICATE_MESSAGE);
				}
			);
		}

		{
			// valid (second, from a)
			overseer_send(
				&mut virtual_overseer,
				AvailabilityDistributionMessage::NetworkBridgeUpdateV1(
					NetworkBridgeEvent::PeerMessage(
						peer_a.clone(),
						chunk_protocol_message(valid.clone()),
					),
				),
			)
			.await;

			assert_matches!(
				overseer_recv(&mut virtual_overseer).await,
				AllMessages::NetworkBridge(
					NetworkBridgeMessage::ReportPeer(
						peer,
						rep
					)
				) => {
					assert_eq!(peer, peer_a);
					assert_eq!(rep, BENEFIT_VALID_MESSAGE);
				}
			);
		}

		// peer a is not interested in anything anymore
		overseer_send(
			&mut virtual_overseer,
			AvailabilityDistributionMessage::NetworkBridgeUpdateV1(
				NetworkBridgeEvent::PeerViewChange(peer_a.clone(), view![]),
			),
		)
		.await;

		{
			// send the a message again, so we should detect the duplicate
			overseer_send(
				&mut virtual_overseer,
				AvailabilityDistributionMessage::NetworkBridgeUpdateV1(
					NetworkBridgeEvent::PeerMessage(
						peer_a.clone(),
						chunk_protocol_message(valid.clone()),
					),
				),
			)
			.await;

			assert_matches!(
				overseer_recv(&mut virtual_overseer).await,
				AllMessages::NetworkBridge(
					NetworkBridgeMessage::ReportPeer(
						peer,
						rep
					)
				) => {
					assert_eq!(peer, peer_a);
					assert_eq!(rep, COST_PEER_DUPLICATE_MESSAGE);
				}
			);
		}

		// peer b sends a message before we have the view
		// setup peer a with interest in parent x
		overseer_send(
			&mut virtual_overseer,
			AvailabilityDistributionMessage::NetworkBridgeUpdateV1(
				NetworkBridgeEvent::PeerDisconnected(peer_b.clone()),
			),
		)
		.await;

		delay!(10);

		overseer_send(
			&mut virtual_overseer,
			AvailabilityDistributionMessage::NetworkBridgeUpdateV1(
				NetworkBridgeEvent::PeerConnected(peer_b.clone(), ObservedRole::Full),
			),
		)
		.await;

		{
			// send another message
			let valid2: AvailabilityGossipMessage = make_valid_availability_gossip(
				&test_state,
				candidates[2].hash(),
				1,
				pov_block_c.clone(),
			);

			// send the a message before we send a view update
			overseer_send(
				&mut virtual_overseer,
				AvailabilityDistributionMessage::NetworkBridgeUpdateV1(
					NetworkBridgeEvent::PeerMessage(peer_a.clone(), chunk_protocol_message(valid2)),
				),
			)
			.await;

			assert_matches!(
				overseer_recv(&mut virtual_overseer).await,
				AllMessages::NetworkBridge(
					NetworkBridgeMessage::ReportPeer(
						peer,
						rep
					)
				) => {
					assert_eq!(peer, peer_a);
					assert_eq!(rep, COST_NOT_A_LIVE_CANDIDATE);
				}
			);
		}
	});
}

#[test]
fn k_ancestors_in_session() {
	let pool = sp_core::testing::TaskExecutor::new();
	let (mut ctx, mut virtual_overseer) =
		test_helpers::make_subsystem_context::<AvailabilityDistributionMessage, _>(pool);

	const DATA: &[(Hash, SessionIndex)] = &[
		(Hash::repeat_byte(0x32), 3), // relay parent
		(Hash::repeat_byte(0x31), 3), // grand parent
		(Hash::repeat_byte(0x30), 3), // great ...
		(Hash::repeat_byte(0x20), 2),
		(Hash::repeat_byte(0x12), 1),
		(Hash::repeat_byte(0x11), 1),
		(Hash::repeat_byte(0x10), 1),
	];
	const K: usize = 5;

	const EXPECTED: &[Hash] = &[DATA[1].0, DATA[2].0];

	let test_fut = async move {
		assert_matches!(
			overseer_recv(&mut virtual_overseer).await,
			AllMessages::ChainApi(ChainApiMessage::Ancestors {
				hash: relay_parent,
				k,
				response_channel: tx,
			}) => {
				assert_eq!(k, K+1);
				assert_eq!(relay_parent, DATA[0].0);
				tx.send(Ok(DATA[1..=k].into_iter().map(|x| x.0).collect::<Vec<_>>())).unwrap();
			}
		);

		// query the desired session index of the relay parent
		assert_matches!(
			overseer_recv(&mut virtual_overseer).await,
			AllMessages::RuntimeApi(RuntimeApiMessage::Request(
				relay_parent,
				RuntimeApiRequest::SessionIndexForChild(tx),
			)) => {
				assert_eq!(relay_parent, DATA[0].0);
				let session: SessionIndex = DATA[0].1;
				tx.send(Ok(session)).unwrap();
			}
		);

		// query ancestors
		for i in 2usize..=(EXPECTED.len() + 1 + 1) {
			assert_matches!(
				overseer_recv(&mut virtual_overseer).await,
				AllMessages::RuntimeApi(RuntimeApiMessage::Request(
					relay_parent,
					RuntimeApiRequest::SessionIndexForChild(tx),
				)) => {
					// query is for ancestor_parent
					let x = &DATA[i];
					assert_eq!(relay_parent, x.0);
					// but needs to yield ancestor_parent's child's session index
					let x = &DATA[i-1];
					tx.send(Ok(x.1)).unwrap();
				}
			);
		}
	};

	let sut = async move {
		let ancestors = query_up_to_k_ancestors_in_same_session(&mut ctx, DATA[0].0, K)
			.await
			.unwrap();
		assert_eq!(ancestors, EXPECTED.to_vec());
	};

	futures::pin_mut!(test_fut);
	futures::pin_mut!(sut);

	executor::block_on(future::join(test_fut, sut).timeout(Duration::from_millis(1000)));
}