client.rs

		let justified_header = JustifiedHeader {
			header: header,
			justification,
			authorities: authorities.to_vec(),
		};

		// TODO [rob]: non-instant finality.
		self.import_block(
			BlockOrigin::ConsensusBroadcast,
			justified_header,
			Some(extrinsics),
			true
		).is_ok()
	}
}

impl<B, E, Block> bft::Authorities<Block> for Client<B, E, Block>
	where
		B: backend::Backend<Block, Blake2Hasher>,
		E: CallExecutor<Block, Blake2Hasher>,
		Block: BlockT,
{
	fn authorities(&self, at: &BlockId<Block>) -> Result<Vec<AuthorityId>, bft::Error> {
		let on_chain_version: Result<_, bft::Error> = self.runtime_version_at(at)
			.map_err(|e| { trace!("Error getting runtime version {:?}", e); bft::ErrorKind::RuntimeVersionMissing.into() });
		let on_chain_version = on_chain_version?;
		let native_version: Result<_, bft::Error> = self.executor.native_runtime_version()
			.ok_or_else(|| bft::ErrorKind::NativeRuntimeMissing.into());
		let native_version = native_version?;
		if !native_version.can_author_with(&on_chain_version) {
			return Err(bft::ErrorKind::IncompatibleAuthoringRuntime(on_chain_version, native_version.runtime_version.clone()).into())
		}
		self.authorities_at(at).map_err(|_| {
			let descriptor = format!("{:?}", at);
			bft::ErrorKind::StateUnavailable(descriptor).into()
		})
	}
}

impl<B, E, Block> BlockchainEvents<Block> for Client<B, E, Block>
where
	E: CallExecutor<Block, Blake2Hasher>,
	Block: BlockT,
{
	/// Get block import event stream.
	fn import_notification_stream(&self) -> ImportNotifications<Block> {
		let (sink, stream) = mpsc::unbounded();
		self.import_notification_sinks.lock().push(sink);
		stream
	}

	fn finality_notification_stream(&self) -> FinalityNotifications<Block> {
		let (sink, stream) = mpsc::unbounded();
		self.finality_notification_sinks.lock().push(sink);
		stream
	}

	/// Get storage changes event stream.
	fn storage_changes_notification_stream(&self, filter_keys: Option<&[StorageKey]>) -> error::Result<StorageEventStream<Block::Hash>> {
		Ok(self.storage_notifications.lock().listen(filter_keys))
	}
}

impl<B, E, Block> ChainHead<Block> for Client<B, E, Block>
where
	B: backend::Backend<Block, Blake2Hasher>,
	E: CallExecutor<Block, Blake2Hasher>,
	Block: BlockT,
{
	fn best_block_header(&self) -> error::Result<<Block as BlockT>::Header> {
		Client::best_block_header(self)
	}
}

impl<B, E, Block> BlockBody<Block> for Client<B, E, Block>
	where
		B: backend::Backend<Block, Blake2Hasher>,
		E: CallExecutor<Block, Blake2Hasher>,
		Block: BlockT,
{
	fn block_body(&self, id: &BlockId<Block>) -> error::Result<Option<Vec<<Block as BlockT>::Extrinsic>>> {
		self.body(id)
	}
}

impl<B, E, Block> api::Core<Block, AuthorityId> for Client<B, E, Block> where
	B: backend::Backend<Block, Blake2Hasher>,
	E: CallExecutor<Block, Blake2Hasher>,
	Block: BlockT,
{
	type Error = Error;

	fn version(&self, at: &BlockId<Block>) -> Result<RuntimeVersion, Self::Error> {
		self.call_api_at(at, "version", &())
	}

	fn authorities(&self, at: &BlockId<Block>) -> Result<Vec<AuthorityId>, Self::Error> {
		bft::Authorities::authorities(self, at).map_err(Into::into)
	}

	fn execute_block(&self, at: &BlockId<Block>, block: &Block) -> Result<(), Self::Error> {
		self.call_api_at(at, "execute_block", &(block))
	}
}

impl<B, E, Block> api::Metadata<Block> for Client<B, E, Block> where
	B: backend::Backend<Block, Blake2Hasher>,
	E: CallExecutor<Block, Blake2Hasher>,
	Block: BlockT,
{
	type Error = Error;

	fn metadata(&self, at: &BlockId<Block>) -> Result<Vec<u8>, Self::Error> {
		self.call_api_at(at, "metadata", &())
	}
}

impl<B, E, Block> api::BlockBuilder<Block> for Client<B, E, Block> where
	B: backend::Backend<Block, Blake2Hasher>,
	E: CallExecutor<Block, Blake2Hasher>,
	Block: BlockT,
{
	type Error = Error;
	type OverlayedChanges = OverlayedChanges;

	fn initialise_block(
		&self,
		at: &BlockId<Block>,
		changes: &mut OverlayedChanges,
		header: &<Block as BlockT>::Header
	) -> Result<(), Self::Error> {
		self.call_at_state(at, "initialise_block", header, changes)
	}

	fn apply_extrinsic(
		&self,
		at: &BlockId<Block>,
		changes: &mut OverlayedChanges,
		extrinsic: &<Block as BlockT>::Extrinsic
	) -> Result<ApplyResult, Self::Error> {
		self.call_at_state(at, "apply_extrinsic", extrinsic, changes)
	}

	fn finalise_block(
		&self,
		at: &BlockId<Block>,
		changes: &mut OverlayedChanges
	) -> Result<<Block as BlockT>::Header, Self::Error> {
		self.call_at_state(at, "finalise_block", &(), changes)
	}

	fn inherent_extrinsics<InherentExtrinsic: Encode + Decode, UncheckedExtrinsic: Encode + Decode>(
		&self, at: &BlockId<Block>, inherent: &InherentExtrinsic
	) -> Result<Vec<UncheckedExtrinsic>, Self::Error> {
		self.call_api_at(at, "inherent_extrinsics", &(inherent))
	}

	fn random_seed(&self, at: &BlockId<Block>) -> Result<<Block as BlockT>::Hash, Self::Error> {
		self.call_api_at(at, "random_seed", &())
	}
}

impl<B, E, Block> api::OldTxQueue<Block> for Client<B, E, Block> where
	B: backend::Backend<Block, Blake2Hasher>,
	E: CallExecutor<Block, Blake2Hasher>,
	Block: BlockT,
{
	type Error = Error;

	fn account_nonce<AccountId: Encode + Decode, Index: Encode + Decode>(
		&self, at: &BlockId<Block>, account: &AccountId
	) -> Result<Index, Self::Error> {
		self.call_api_at(at, "account_nonce", &(account))
	}

	fn lookup_address<Address: Encode + Decode, AccountId: Encode + Decode>(
		&self, at: &BlockId<Block>, address: &Address
	) -> Result<Option<AccountId>, Self::Error> {
		self.call_api_at(at, "lookup_address", &(address))
	}
}

impl<B, E, Block> api::TaggedTransactionQueue<Block> for Client<B, E, Block> where
	B: backend::Backend<Block, Blake2Hasher>,
	E: CallExecutor<Block, Blake2Hasher>,
	Block: BlockT,
{
	type Error = Error;

	fn validate_transaction<TransactionValidity: Encode + Decode>(
		&self, at: &BlockId<Block>, tx: &<Block as BlockT>::Extrinsic
	) -> Result<TransactionValidity, Self::Error> {
		self.call_api_at(at, "validate_transaction", &(tx))
	}
}

impl<B, E, Block> api::Miscellaneous<Block> for Client<B, E, Block> where
	B: backend::Backend<Block, Blake2Hasher>,
	E: CallExecutor<Block, Blake2Hasher>,
	Block: BlockT,
{
	type Error = Error;

	fn validator_count(&self, at: &BlockId<Block>) -> Result<u32, Self::Error> {
		self.call_api_at(at, "validator_count", &())
	}

	fn validators<AccountId: Encode + Decode>(
		&self, at: &BlockId<Block>
	) -> Result<Vec<AccountId>, Self::Error> {
		self.call_api_at(at, "validators", &())
	}

	fn timestamp<Moment: Encode + Decode>(
		&self, at: &BlockId<Block>
	) -> Result<Moment, Self::Error> {
		self.call_api_at(at, "timestamp", &())
	}
}

#[cfg(test)]
pub(crate) mod tests {
	use std::collections::HashMap;
	use super::*;
	use keyring::Keyring;
	use primitives::twox_128;
	use runtime_primitives::traits::{Digest as DigestT, DigestItem as DigestItemT};
	use runtime_primitives::generic::DigestItem;
	use test_client::{self, TestClient};
	use test_client::client::BlockOrigin;
	use test_client::client::backend::Backend as TestBackend;
	use test_client::BlockBuilderExt;
	use test_client::runtime::{self, Block, Transfer};

	/// Returns tuple, consisting of:
	/// 1) test client pre-filled with blocks changing balances;
	/// 2) roots of changes tries for these blocks
	/// 3) test cases in form (begin, end, key, vec![(block, extrinsic)]) that are required to pass
	pub fn prepare_client_with_key_changes() -> (
		test_client::client::Client<test_client::Backend, test_client::Executor, Block>,
		Vec<H256>,
		Vec<(u64, u64, Vec<u8>, Vec<(u64, u32)>)>,
	) {
		// prepare block structure
		let blocks_transfers = vec![
			vec![(Keyring::Alice, Keyring::Dave), (Keyring::Bob, Keyring::Dave)],
			vec![(Keyring::Charlie, Keyring::Eve)],
			vec![],
			vec![(Keyring::Alice, Keyring::Dave)],
		];

		// prepare client ang import blocks
		let mut local_roots = Vec::new();
		let remote_client = test_client::new_with_changes_trie();
		let mut nonces: HashMap<_, u64> = Default::default();
		for (i, block_transfers) in blocks_transfers.into_iter().enumerate() {
			let mut builder = remote_client.new_block().unwrap();
			for (from, to) in block_transfers {
				builder.push_transfer(Transfer {
					from: from.to_raw_public().into(),
					to: to.to_raw_public().into(),
					amount: 1,
					nonce: *nonces.entry(from).and_modify(|n| { *n = *n + 1 }).or_default(),
				}).unwrap();
			}
			remote_client.justify_and_import(BlockOrigin::Own, builder.bake().unwrap()).unwrap();

			let header = remote_client.header(&BlockId::Number(i as u64 + 1)).unwrap().unwrap();
			let trie_root = header.digest().log(DigestItem::as_changes_trie_root)
				.map(|root| H256::from_slice(root.as_ref()))
				.unwrap();
			local_roots.push(trie_root);
		}

		// prepare test cases
		let alice = twox_128(&runtime::system::balance_of_key(Keyring::Alice.to_raw_public().into())).to_vec();
		let bob = twox_128(&runtime::system::balance_of_key(Keyring::Bob.to_raw_public().into())).to_vec();
		let charlie = twox_128(&runtime::system::balance_of_key(Keyring::Charlie.to_raw_public().into())).to_vec();
		let dave = twox_128(&runtime::system::balance_of_key(Keyring::Dave.to_raw_public().into())).to_vec();
		let eve = twox_128(&runtime::system::balance_of_key(Keyring::Eve.to_raw_public().into())).to_vec();
		let ferdie = twox_128(&runtime::system::balance_of_key(Keyring::Ferdie.to_raw_public().into())).to_vec();
		let test_cases = vec![
			(1, 4, alice.clone(), vec![(4, 0), (1, 0)]),
			(1, 3, alice.clone(), vec![(1, 0)]),
			(2, 4, alice.clone(), vec![(4, 0)]),
			(2, 3, alice.clone(), vec![]),

			(1, 4, bob.clone(), vec![(1, 1)]),
			(1, 1, bob.clone(), vec![(1, 1)]),
			(2, 4, bob.clone(), vec![]),

			(1, 4, charlie.clone(), vec![(2, 0)]),

			(1, 4, dave.clone(), vec![(4, 0), (1, 1), (1, 0)]),
			(1, 1, dave.clone(), vec![(1, 1), (1, 0)]),
			(3, 4, dave.clone(), vec![(4, 0)]),

			(1, 4, eve.clone(), vec![(2, 0)]),
			(1, 1, eve.clone(), vec![]),
			(3, 4, eve.clone(), vec![]),

			(1, 4, ferdie.clone(), vec![]),
		];

		(remote_client, local_roots, test_cases)
	}

	#[test]
	fn client_initialises_from_genesis_ok() {
		let client = test_client::new();

		assert_eq!(client.call_api::<_, u64>("balance_of", &Keyring::Alice.to_raw_public()).unwrap(), 1000);
		assert_eq!(client.call_api::<_, u64>("balance_of", &Keyring::Ferdie.to_raw_public()).unwrap(), 0);
	}

	#[test]
	fn authorities_call_works() {
		let client = test_client::new();

		assert_eq!(client.info().unwrap().chain.best_number, 0);
		assert_eq!(client.authorities_at(&BlockId::Number(0)).unwrap(), vec![
			Keyring::Alice.to_raw_public().into(),
			Keyring::Bob.to_raw_public().into(),
			Keyring::Charlie.to_raw_public().into()
		]);
	}

	#[test]
	fn block_builder_works_with_no_transactions() {
		let client = test_client::new();

		let builder = client.new_block().unwrap();

		client.justify_and_import(BlockOrigin::Own, builder.bake().unwrap()).unwrap();

		assert_eq!(client.info().unwrap().chain.best_number, 1);
	}

	#[test]
	fn block_builder_works_with_transactions() {
		let client = test_client::new();

		let mut builder = client.new_block().unwrap();

		builder.push_transfer(Transfer {
			from: Keyring::Alice.to_raw_public().into(),
			to: Keyring::Ferdie.to_raw_public().into(),
			amount: 42,
			nonce: 0,
		}).unwrap();

		client.justify_and_import(BlockOrigin::Own, builder.bake().unwrap()).unwrap();

		assert_eq!(client.info().unwrap().chain.best_number, 1);
		assert!(client.state_at(&BlockId::Number(1)).unwrap() != client.state_at(&BlockId::Number(0)).unwrap());
		assert_eq!(client.call_api::<_, u64>("balance_of", &Keyring::Alice.to_raw_public()).unwrap(), 958);
		assert_eq!(client.call_api::<_, u64>("balance_of", &Keyring::Ferdie.to_raw_public()).unwrap(), 42);
	}

	#[test]
	fn client_uses_authorities_from_blockchain_cache() {
		let client = test_client::new();
		test_client::client::in_mem::cache_authorities_at(
			client.backend().blockchain(),
			Default::default(),
			Some(vec![[1u8; 32].into()]));
		assert_eq!(client.authorities_at(
			&BlockId::Hash(Default::default())).unwrap(),
			vec![[1u8; 32].into()]);
	}

	#[test]
	fn block_builder_does_not_include_invalid() {
		let client = test_client::new();

		let mut builder = client.new_block().unwrap();

		builder.push_transfer(Transfer {
			from: Keyring::Alice.to_raw_public().into(),
			to: Keyring::Ferdie.to_raw_public().into(),
			amount: 42,
			nonce: 0,
		}).unwrap();

		assert!(builder.push_transfer(Transfer {
			from: Keyring::Eve.to_raw_public().into(),
			to: Keyring::Alice.to_raw_public().into(),
			amount: 42,
			nonce: 0,
		}).is_err());

		client.justify_and_import(BlockOrigin::Own, builder.bake().unwrap()).unwrap();

		assert_eq!(client.info().unwrap().chain.best_number, 1);
		assert!(client.state_at(&BlockId::Number(1)).unwrap() != client.state_at(&BlockId::Number(0)).unwrap());
		assert_eq!(client.body(&BlockId::Number(1)).unwrap().unwrap().len(), 1)
	}

	#[test]
	fn best_containing_with_genesis_block() {
		// block tree:
		// G

		let client = test_client::new();

		let genesis_hash = client.info().unwrap().chain.genesis_hash;

		assert_eq!(genesis_hash.clone(), client.best_containing(genesis_hash.clone(), None).unwrap().unwrap());
	}

	#[test]
	fn best_containing_with_hash_not_found() {
		// block tree:
		// G

		let client = test_client::new();

		let uninserted_block = client.new_block().unwrap().bake().unwrap();

		assert_eq!(None, client.best_containing(uninserted_block.hash().clone(), None).unwrap());
	}

	#[test]
	fn best_containing_with_single_chain_3_blocks() {
		// block tree:
		// G -> A1 -> A2

		let client = test_client::new();

		// G -> A1
		let a1 = client.new_block().unwrap().bake().unwrap();
		client.justify_and_import(BlockOrigin::Own, a1.clone()).unwrap();

		// A1 -> A2
		let a2 = client.new_block().unwrap().bake().unwrap();
		client.justify_and_import(BlockOrigin::Own, a2.clone()).unwrap();

		let genesis_hash = client.info().unwrap().chain.genesis_hash;

		assert_eq!(a2.hash(), client.best_containing(genesis_hash, None).unwrap().unwrap());
		assert_eq!(a2.hash(), client.best_containing(a1.hash(), None).unwrap().unwrap());
		assert_eq!(a2.hash(), client.best_containing(a2.hash(), None).unwrap().unwrap());
	}

	#[test]
	fn best_containing_with_multiple_forks() {
		// NOTE: we use the version of the trait from `test_client`
		// because that is actually different than the version linked to
		// in the test facade crate.
		use test_client::blockchain::Backend as BlockchainBackendT;

		// block tree:
		// G -> A1 -> A2 -> A3 -> A4 -> A5
		//      A1 -> B2 -> B3 -> B4
		//	          B2 -> C3
		//	    A1 -> D2
		let client = test_client::new();

		// G -> A1
		let a1 = client.new_block().unwrap().bake().unwrap();
		client.justify_and_import(BlockOrigin::Own, a1.clone()).unwrap();

		// A1 -> A2
		let a2 = client.new_block_at(&BlockId::Hash(a1.hash())).unwrap().bake().unwrap();
		client.justify_and_import(BlockOrigin::Own, a2.clone()).unwrap();

		// A2 -> A3
		let a3 = client.new_block_at(&BlockId::Hash(a2.hash())).unwrap().bake().unwrap();
		client.justify_and_import(BlockOrigin::Own, a3.clone()).unwrap();

		// A3 -> A4
		let a4 = client.new_block_at(&BlockId::Hash(a3.hash())).unwrap().bake().unwrap();
		client.justify_and_import(BlockOrigin::Own, a4.clone()).unwrap();

		// A4 -> A5
		let a5 = client.new_block_at(&BlockId::Hash(a4.hash())).unwrap().bake().unwrap();
		client.justify_and_import(BlockOrigin::Own, a5.clone()).unwrap();

		// A1 -> B2
		let mut builder = client.new_block_at(&BlockId::Hash(a1.hash())).unwrap();
		// this push is required as otherwise B2 has the same hash as A2 and won't get imported
		builder.push_transfer(Transfer {
			from: Keyring::Alice.to_raw_public().into(),
			to: Keyring::Ferdie.to_raw_public().into(),
			amount: 41,
			nonce: 0,
		}).unwrap();
		let b2 = builder.bake().unwrap();
		client.justify_and_import(BlockOrigin::Own, b2.clone()).unwrap();

		// B2 -> B3
		let b3 = client.new_block_at(&BlockId::Hash(b2.hash())).unwrap().bake().unwrap();
		client.justify_and_import(BlockOrigin::Own, b3.clone()).unwrap();

		// B3 -> B4
		let b4 = client.new_block_at(&BlockId::Hash(b3.hash())).unwrap().bake().unwrap();
		client.justify_and_import(BlockOrigin::Own, b4.clone()).unwrap();

		// // B2 -> C3
		let mut builder = client.new_block_at(&BlockId::Hash(b2.hash())).unwrap();
		// this push is required as otherwise C3 has the same hash as B3 and won't get imported
		builder.push_transfer(Transfer {
			from: Keyring::Alice.to_raw_public().into(),
			to: Keyring::Ferdie.to_raw_public().into(),
			amount: 1,
			nonce: 1,
		}).unwrap();
		let c3 = builder.bake().unwrap();
		client.justify_and_import(BlockOrigin::Own, c3.clone()).unwrap();

		// A1 -> D2
		let mut builder = client.new_block_at(&BlockId::Hash(a1.hash())).unwrap();
		// this push is required as otherwise D2 has the same hash as B2 and won't get imported
		builder.push_transfer(Transfer {
			from: Keyring::Alice.to_raw_public().into(),
			to: Keyring::Ferdie.to_raw_public().into(),
			amount: 1,
			nonce: 0,
		}).unwrap();
		let d2 = builder.bake().unwrap();
		client.justify_and_import(BlockOrigin::Own, d2.clone()).unwrap();

		assert_eq!(client.info().unwrap().chain.best_hash, a5.hash());

		let genesis_hash = client.info().unwrap().chain.genesis_hash;
		let leaves = BlockchainBackendT::leaves(client.backend().blockchain()).unwrap();

		assert!(leaves.contains(&a5.hash()));
		assert!(leaves.contains(&b4.hash()));
		assert!(leaves.contains(&c3.hash()));
		assert!(leaves.contains(&d2.hash()));
		assert_eq!(leaves.len(), 4);

		// search without restriction

		assert_eq!(a5.hash(), client.best_containing(genesis_hash, None).unwrap().unwrap());
		assert_eq!(a5.hash(), client.best_containing(a1.hash(), None).unwrap().unwrap());
		assert_eq!(a5.hash(), client.best_containing(a2.hash(), None).unwrap().unwrap());
		assert_eq!(a5.hash(), client.best_containing(a3.hash(), None).unwrap().unwrap());
		assert_eq!(a5.hash(), client.best_containing(a4.hash(), None).unwrap().unwrap());
		assert_eq!(a5.hash(), client.best_containing(a5.hash(), None).unwrap().unwrap());

		assert_eq!(b4.hash(), client.best_containing(b2.hash(), None).unwrap().unwrap());
		assert_eq!(b4.hash(), client.best_containing(b3.hash(), None).unwrap().unwrap());
		assert_eq!(b4.hash(), client.best_containing(b4.hash(), None).unwrap().unwrap());

		assert_eq!(c3.hash(), client.best_containing(c3.hash(), None).unwrap().unwrap());

		assert_eq!(d2.hash(), client.best_containing(d2.hash(), None).unwrap().unwrap());


		// search only blocks with number <= 5. equivalent to without restriction for this scenario

		assert_eq!(a5.hash(), client.best_containing(genesis_hash, Some(5)).unwrap().unwrap());
		assert_eq!(a5.hash(), client.best_containing(a1.hash(), Some(5)).unwrap().unwrap());
		assert_eq!(a5.hash(), client.best_containing(a2.hash(), Some(5)).unwrap().unwrap());
		assert_eq!(a5.hash(), client.best_containing(a3.hash(), Some(5)).unwrap().unwrap());
		assert_eq!(a5.hash(), client.best_containing(a4.hash(), Some(5)).unwrap().unwrap());
		assert_eq!(a5.hash(), client.best_containing(a5.hash(), Some(5)).unwrap().unwrap());

		assert_eq!(b4.hash(), client.best_containing(b2.hash(), Some(5)).unwrap().unwrap());
		assert_eq!(b4.hash(), client.best_containing(b3.hash(), Some(5)).unwrap().unwrap());
		assert_eq!(b4.hash(), client.best_containing(b4.hash(), Some(5)).unwrap().unwrap());

		assert_eq!(c3.hash(), client.best_containing(c3.hash(), Some(5)).unwrap().unwrap());

		assert_eq!(d2.hash(), client.best_containing(d2.hash(), Some(5)).unwrap().unwrap());


		// search only blocks with number <= 4

		assert_eq!(a4.hash(), client.best_containing(genesis_hash, Some(4)).unwrap().unwrap());
		assert_eq!(a4.hash(), client.best_containing(a1.hash(), Some(4)).unwrap().unwrap());
		assert_eq!(a4.hash(), client.best_containing(a2.hash(), Some(4)).unwrap().unwrap());
		assert_eq!(a4.hash(), client.best_containing(a3.hash(), Some(4)).unwrap().unwrap());
		assert_eq!(a4.hash(), client.best_containing(a4.hash(), Some(4)).unwrap().unwrap());
		assert_eq!(None, client.best_containing(a5.hash(), Some(4)).unwrap());

		assert_eq!(b4.hash(), client.best_containing(b2.hash(), Some(4)).unwrap().unwrap());
		assert_eq!(b4.hash(), client.best_containing(b3.hash(), Some(4)).unwrap().unwrap());
		assert_eq!(b4.hash(), client.best_containing(b4.hash(), Some(4)).unwrap().unwrap());

		assert_eq!(c3.hash(), client.best_containing(c3.hash(), Some(4)).unwrap().unwrap());

		assert_eq!(d2.hash(), client.best_containing(d2.hash(), Some(4)).unwrap().unwrap());


		// search only blocks with number <= 3

		assert_eq!(a3.hash(), client.best_containing(genesis_hash, Some(3)).unwrap().unwrap());
		assert_eq!(a3.hash(), client.best_containing(a1.hash(), Some(3)).unwrap().unwrap());
		assert_eq!(a3.hash(), client.best_containing(a2.hash(), Some(3)).unwrap().unwrap());
		assert_eq!(a3.hash(), client.best_containing(a3.hash(), Some(3)).unwrap().unwrap());
		assert_eq!(None, client.best_containing(a4.hash(), Some(3)).unwrap());
		assert_eq!(None, client.best_containing(a5.hash(), Some(3)).unwrap());

		assert_eq!(b3.hash(), client.best_containing(b2.hash(), Some(3)).unwrap().unwrap());
		assert_eq!(b3.hash(), client.best_containing(b3.hash(), Some(3)).unwrap().unwrap());
		assert_eq!(None, client.best_containing(b4.hash(), Some(3)).unwrap());

		assert_eq!(c3.hash(), client.best_containing(c3.hash(), Some(3)).unwrap().unwrap());

		assert_eq!(d2.hash(), client.best_containing(d2.hash(), Some(3)).unwrap().unwrap());


		// search only blocks with number <= 2

		assert_eq!(a2.hash(), client.best_containing(genesis_hash, Some(2)).unwrap().unwrap());
		assert_eq!(a2.hash(), client.best_containing(a1.hash(), Some(2)).unwrap().unwrap());
		assert_eq!(a2.hash(), client.best_containing(a2.hash(), Some(2)).unwrap().unwrap());
		assert_eq!(None, client.best_containing(a3.hash(), Some(2)).unwrap());
		assert_eq!(None, client.best_containing(a4.hash(), Some(2)).unwrap());
		assert_eq!(None, client.best_containing(a5.hash(), Some(2)).unwrap());

		assert_eq!(b2.hash(), client.best_containing(b2.hash(), Some(2)).unwrap().unwrap());
		assert_eq!(None, client.best_containing(b3.hash(), Some(2)).unwrap());
		assert_eq!(None, client.best_containing(b4.hash(), Some(2)).unwrap());

		assert_eq!(None, client.best_containing(c3.hash(), Some(2)).unwrap());

		assert_eq!(d2.hash(), client.best_containing(d2.hash(), Some(2)).unwrap().unwrap());


		// search only blocks with number <= 1

		assert_eq!(a1.hash(), client.best_containing(genesis_hash, Some(1)).unwrap().unwrap());
		assert_eq!(a1.hash(), client.best_containing(a1.hash(), Some(1)).unwrap().unwrap());
		assert_eq!(None, client.best_containing(a2.hash(), Some(1)).unwrap());
		assert_eq!(None, client.best_containing(a3.hash(), Some(1)).unwrap());
		assert_eq!(None, client.best_containing(a4.hash(), Some(1)).unwrap());
		assert_eq!(None, client.best_containing(a5.hash(), Some(1)).unwrap());

		assert_eq!(None, client.best_containing(b2.hash(), Some(1)).unwrap());
		assert_eq!(None, client.best_containing(b3.hash(), Some(1)).unwrap());
		assert_eq!(None, client.best_containing(b4.hash(), Some(1)).unwrap());

		assert_eq!(None, client.best_containing(c3.hash(), Some(1)).unwrap());

		assert_eq!(None, client.best_containing(d2.hash(), Some(1)).unwrap());

		// search only blocks with number <= 0

		assert_eq!(genesis_hash, client.best_containing(genesis_hash, Some(0)).unwrap().unwrap());
		assert_eq!(None, client.best_containing(a1.hash(), Some(0)).unwrap());
		assert_eq!(None, client.best_containing(a2.hash(), Some(0)).unwrap());
		assert_eq!(None, client.best_containing(a3.hash(), Some(0)).unwrap());
		assert_eq!(None, client.best_containing(a4.hash(), Some(0)).unwrap());
		assert_eq!(None, client.best_containing(a5.hash(), Some(0)).unwrap());

		assert_eq!(None, client.best_containing(b2.hash(), Some(0)).unwrap());
		assert_eq!(None, client.best_containing(b3.hash(), Some(0)).unwrap());
		assert_eq!(None, client.best_containing(b4.hash(), Some(0)).unwrap());

		assert_eq!(None, client.best_containing(c3.hash().clone(), Some(0)).unwrap());

		assert_eq!(None, client.best_containing(d2.hash().clone(), Some(0)).unwrap());
	}

	#[test]
	fn key_changes_works() {
		let (client, _, test_cases) = prepare_client_with_key_changes();

		for (index, (begin, end, key, expected_result)) in test_cases.into_iter().enumerate() {
			let begin = client.block_hash(begin).unwrap().unwrap();
			let end = client.block_hash(end).unwrap().unwrap();
			let actual_result = client.key_changes(begin, end, &key).unwrap();
			match actual_result == expected_result {
				true => (),
				false => panic!(format!("Failed test {}: actual = {:?}, expected = {:?}",
					index, actual_result, expected_result)),
			}
		}
	}
}