client.rs

			self.apply_finality_with_block_hash(operation, to_finalize_hash, justification, last_best, notify)
		})
	}

	/// Attempts to revert the chain by `n` blocks. Returns the number of blocks that were
	/// successfully reverted.
	pub fn revert(&self, n: NumberFor<Block>) -> error::Result<NumberFor<Block>> {
		Ok(self.backend.revert(n)?)
	}

	/// Get blockchain info.
	pub fn info(&self) -> error::Result<ClientInfo<Block>> {
		let info = self.backend.blockchain().info().map_err(|e| error::Error::from_blockchain(Box::new(e)))?;
		Ok(ClientInfo {
			chain: info,
			best_queued_hash: None,
			best_queued_number: None,
		})
	}

	/// Get block status.
	pub fn block_status(&self, id: &BlockId<Block>) -> error::Result<BlockStatus> {
		// TODO: more efficient implementation
		if let BlockId::Hash(ref h) = id {
			if self.importing_block.read().as_ref().map_or(false, |importing| h == importing) {
				return Ok(BlockStatus::Queued);
			}
		}
		match self.backend.blockchain().header(*id).map_err(|e| error::Error::from_blockchain(Box::new(e)))?.is_some() {
			true => Ok(BlockStatus::InChain),
			false => Ok(BlockStatus::Unknown),
		}
	}

	/// Get block header by id.
	pub fn header(&self, id: &BlockId<Block>) -> error::Result<Option<<Block as BlockT>::Header>> {
		self.backend.blockchain().header(*id)
	}

	/// Get block body by id.
	pub fn body(&self, id: &BlockId<Block>) -> error::Result<Option<Vec<<Block as BlockT>::Extrinsic>>> {
		self.backend.blockchain().body(*id)
	}

	/// Get block justification set by id.
	pub fn justification(&self, id: &BlockId<Block>) -> error::Result<Option<Justification>> {
		self.backend.blockchain().justification(*id)
	}

	/// Get full block by id.
	pub fn block(&self, id: &BlockId<Block>)
		-> error::Result<Option<SignedBlock<Block>>>
	{
		Ok(match (self.header(id)?, self.body(id)?, self.justification(id)?) {
			(Some(header), Some(extrinsics), justification) =>
				Some(SignedBlock { block: Block::new(header, extrinsics), justification }),
			_ => None,
		})
	}

	/// Get best block header.
	pub fn best_block_header(&self) -> error::Result<<Block as BlockT>::Header> {
		let info = self.backend.blockchain().info().map_err(|e| error::Error::from_blockchain(Box::new(e)))?;
		Ok(self.header(&BlockId::Hash(info.best_hash))?.expect("Best block header must always exist"))
	}

	/// Get the most recent block hash of the best (longest) chains
	/// that contain block with the given `target_hash`.
	///
	/// The search space is always limited to blocks which are in the finalized
	/// chain or descendents of it.
	///
	/// If `maybe_max_block_number` is `Some(max_block_number)`
	/// the search is limited to block `numbers <= max_block_number`.
	/// in other words as if there were no blocks greater `max_block_number`.
	///
	/// TODO [snd] possibly implement this on blockchain::Backend and just redirect here
	/// Returns `Ok(None)` if `target_hash` is not found in search space.
	/// TODO [snd] write down time complexity
	pub fn best_containing(&self, target_hash: Block::Hash, maybe_max_number: Option<NumberFor<Block>>)
		-> error::Result<Option<Block::Hash>>
	{
		let target_header = {
			match self.backend.blockchain().header(BlockId::Hash(target_hash))? {
				Some(x) => x,
				// target not in blockchain
				None => { return Ok(None); },
			}
		};

		if let Some(max_number) = maybe_max_number {
			// target outside search range
			if target_header.number() > &max_number {
				return Ok(None);
			}
		}

		let (leaves, best_already_checked) = {
			// ensure no blocks are imported during this code block.
			// an import could trigger a reorg which could change the canonical chain.
			// we depend on the canonical chain staying the same during this code block.
			let _import_lock = self.import_lock.lock();

			let info = self.backend.blockchain().info()?;

			let canon_hash = self.backend.blockchain().hash(*target_header.number())?
				.ok_or_else(|| error::Error::from(format!("failed to get hash for block number {}", target_header.number())))?;

			if canon_hash == target_hash {
				// if no block at the given max depth exists fallback to the best block
				if let Some(max_number) = maybe_max_number {
					if let Some(header) = self.backend.blockchain().hash(max_number)? {
						return Ok(Some(header));
					}
				}

				return Ok(Some(info.best_hash));
			} else if info.finalized_number >= *target_header.number() {
				// header is on a dead fork.
				return Ok(None);
			}

			(self.backend.blockchain().leaves()?, info.best_hash)
		};

		// for each chain. longest chain first. shortest last
		for leaf_hash in leaves {
			// ignore canonical chain which we already checked above
			if leaf_hash == best_already_checked {
				continue;
			}

			// start at the leaf
			let mut current_hash = leaf_hash;

			// if search is not restricted then the leaf is the best
			let mut best_hash = leaf_hash;

			// go backwards entering the search space
			// waiting until we are <= max_number
			if let Some(max_number) = maybe_max_number {
				loop {
					// TODO [snd] this should be a panic
					let current_header = self.backend.blockchain().header(BlockId::Hash(current_hash.clone()))?
						.ok_or_else(|| error::Error::from(format!("failed to get header for hash {}", current_hash)))?;

					if current_header.number() <= &max_number {
						best_hash = current_header.hash();
						break;
					}

					current_hash = *current_header.parent_hash();
				}
			}

			// go backwards through the chain (via parent links)
			loop {
				// until we find target
				if current_hash == target_hash {
					return Ok(Some(best_hash));
				}

				// TODO [snd] this should be a panic
				let current_header = self.backend.blockchain().header(BlockId::Hash(current_hash.clone()))?
					.ok_or_else(|| error::Error::from(format!("failed to get header for hash {}", current_hash)))?;

				// stop search in this chain once we go below the target's block number
				if current_header.number() < target_header.number() {
					break;
				}

				current_hash = *current_header.parent_hash();
			}
		}

		// header may be on a dead fork -- the only leaves that are considered are
		// those which can still be finalized.
		//
		// TODO: only issue this warning when not on a dead fork
		// part of https://github.com/paritytech/substrate/issues/1558
		warn!(
			"Block {:?} exists in chain but not found when following all \
			leaves backwards. Number limit = {:?}",
			target_hash,
			maybe_max_number,
		);

		Ok(None)
	}

	fn changes_trie_config(&self) -> Result<Option<ChangesTrieConfiguration>, Error> {
		Ok(self.backend.state_at(BlockId::Number(self.backend.blockchain().info()?.best_number))?
			.storage(well_known_keys::CHANGES_TRIE_CONFIG)
			.map_err(|e| error::Error::from_state(Box::new(e)))?
			.and_then(|c| Decode::decode(&mut &*c)))
	}

	/// Prepare in-memory header that is used in execution environment.
	fn prepare_environment_block(&self, parent: &BlockId<Block>) -> error::Result<Block::Header> {
		Ok(<<Block as BlockT>::Header as HeaderT>::new(
			self.backend.blockchain().expect_block_number_from_id(parent)? + As::sa(1),
			Default::default(),
			Default::default(),
			self.backend.blockchain().expect_block_hash_from_id(&parent)?,
			Default::default(),
		))
	}
}

impl<B, E, Block, RA> ChainHeaderBackend<Block> for Client<B, E, Block, RA> where
	B: backend::Backend<Block, Blake2Hasher>,
	E: CallExecutor<Block, Blake2Hasher> + Send + Sync,
	Block: BlockT<Hash=H256>,
	RA: Send + Sync
{
	fn header(&self, id: BlockId<Block>) -> error::Result<Option<Block::Header>> {
		self.backend.blockchain().header(id)
	}

	fn info(&self) -> error::Result<blockchain::Info<Block>> {
		self.backend.blockchain().info()
	}

	fn status(&self, id: BlockId<Block>) -> error::Result<blockchain::BlockStatus> {
		self.backend.blockchain().status(id)
	}

	fn number(&self, hash: Block::Hash) -> error::Result<Option<<<Block as BlockT>::Header as HeaderT>::Number>> {
		self.backend.blockchain().number(hash)
	}

	fn hash(&self, number: NumberFor<Block>) -> error::Result<Option<Block::Hash>> {
		self.backend.blockchain().hash(number)
	}
}

impl<B, E, Block, RA> ProvideRuntimeApi for Client<B, E, Block, RA> where
	B: backend::Backend<Block, Blake2Hasher>,
	E: CallExecutor<Block, Blake2Hasher> + Clone + Send + Sync,
	Block: BlockT<Hash=H256>,
	RA: ConstructRuntimeApi<Block, Self>
{
	type Api = <RA as ConstructRuntimeApi<Block, Self>>::RuntimeApi;

	fn runtime_api<'a>(&'a self) -> ApiRef<'a, Self::Api> {
		RA::construct_runtime_api(self)
	}
}

impl<B, E, Block, RA> CallRuntimeAt<Block> for Client<B, E, Block, RA> where
	B: backend::Backend<Block, Blake2Hasher>,
	E: CallExecutor<Block, Blake2Hasher> + Clone + Send + Sync,
	Block: BlockT<Hash=H256>
{
	fn call_api_at<R: Encode + Decode + PartialEq, NC: FnOnce() -> R + UnwindSafe>(
		&self,
		at: &BlockId<Block>,
		function: &'static str,
		args: Vec<u8>,
		changes: &mut OverlayedChanges,
		initialised_block: &mut Option<BlockId<Block>>,
		native_call: Option<NC>,
	) -> error::Result<NativeOrEncoded<R>> {
		let execution_manager = match self.api_execution_strategy {
			ExecutionStrategy::NativeWhenPossible => ExecutionManager::NativeWhenPossible,
			ExecutionStrategy::AlwaysWasm => ExecutionManager::AlwaysWasm,
			ExecutionStrategy::Both => ExecutionManager::Both(|wasm_result, native_result| {
				warn!("Consensus error between wasm and native runtime execution at block {:?}", at);
				warn!("   Function {:?}", function);
				warn!("   Native result {:?}", native_result);
				warn!("   Wasm result {:?}", wasm_result);
				wasm_result
			}),
		};

		self.executor.contextual_call(
			at,
			function,
			&args,
			changes,
			initialised_block,
			|| self.prepare_environment_block(at),
			execution_manager,
			native_call,
		)
	}

	fn runtime_version_at(&self, at: &BlockId<Block>) -> error::Result<RuntimeVersion> {
		self.runtime_version_at(at)
	}
}

impl<B, E, Block, RA> consensus::BlockImport<Block> for Client<B, E, Block, RA> where
	B: backend::Backend<Block, Blake2Hasher>,
	E: CallExecutor<Block, Blake2Hasher> + Clone + Send + Sync,
	Block: BlockT<Hash=H256>,
{
	type Error = ConsensusError;

	/// Import a checked and validated block. If a justification is provided in
	/// `ImportBlock` then `finalized` *must* be true.
	fn import_block(
		&self,
		import_block: ImportBlock<Block>,
		new_authorities: Option<Vec<AuthorityIdFor<Block>>>,
	) -> Result<ImportResult, Self::Error> {
		self.lock_import_and_run(|operation| {
			self.apply_block(operation, import_block, new_authorities)
		}).map_err(|e| ConsensusErrorKind::ClientImport(e.to_string()).into())
	}
}

impl<B, E, Block, RA> consensus::Authorities<Block> for Client<B, E, Block, RA> where
	B: backend::Backend<Block, Blake2Hasher>,
	E: CallExecutor<Block, Blake2Hasher> + Clone,
	Block: BlockT<Hash=H256>,
{
	type Error = Error;
	fn authorities(&self, at: &BlockId<Block>) -> Result<Vec<AuthorityIdFor<Block>>, Self::Error> {
		self.authorities_at(at).map_err(|e| e.into())
	}
}

impl<B, E, Block, RA> CurrentHeight for Client<B, E, Block, RA> where
	B: backend::Backend<Block, Blake2Hasher>,
	E: CallExecutor<Block, Blake2Hasher> + Clone,
	Block: BlockT<Hash=H256>,
{
	type BlockNumber = <Block::Header as HeaderT>::Number;
	fn current_height(&self) -> Self::BlockNumber {
		self.backend.blockchain().info().map(|i| i.best_number).unwrap_or_else(|_| Zero::zero())
	}
}

impl<B, E, Block, RA> BlockNumberToHash for Client<B, E, Block, RA> where
	B: backend::Backend<Block, Blake2Hasher>,
	E: CallExecutor<Block, Blake2Hasher> + Clone,
	Block: BlockT<Hash=H256>,
{
	type BlockNumber = <Block::Header as HeaderT>::Number;
	type Hash = Block::Hash;
	fn block_number_to_hash(&self, n: Self::BlockNumber) -> Option<Self::Hash> {
		self.block_hash(n).unwrap_or(None)
	}
}


impl<B, E, Block, RA> BlockchainEvents<Block> for Client<B, E, Block, RA>
where
	E: CallExecutor<Block, Blake2Hasher>,
	Block: BlockT<Hash=H256>,
{
	/// 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, RA> ChainHead<Block> for Client<B, E, Block, RA>
where
	B: backend::Backend<Block, Blake2Hasher>,
	E: CallExecutor<Block, Blake2Hasher>,
	Block: BlockT<Hash=H256>,
{
	fn best_block_header(&self) -> error::Result<<Block as BlockT>::Header> {
		Client::best_block_header(self)
	}

	fn leaves(&self) -> Result<Vec<<Block as BlockT>::Hash>, error::Error> {
		self.backend.blockchain().leaves()
	}
}

impl<B, E, Block, RA> BlockBody<Block> for Client<B, E, Block, RA>
	where
		B: backend::Backend<Block, Blake2Hasher>,
		E: CallExecutor<Block, Blake2Hasher>,
		Block: BlockT<Hash=H256>,
{
	fn block_body(&self, id: &BlockId<Block>) -> error::Result<Option<Vec<<Block as BlockT>::Extrinsic>>> {
		self.body(id)
	}
}

impl<B, E, Block, RA> backend::AuxStore for Client<B, E, Block, RA>
	where
		B: backend::Backend<Block, Blake2Hasher>,
		E: CallExecutor<Block, Blake2Hasher>,
		Block: BlockT<Hash=H256>,
{
	/// Insert auxiliary data into key-value store.
	fn insert_aux<
		'a,
		'b: 'a,
		'c: 'a,
		I: IntoIterator<Item=&'a(&'c [u8], &'c [u8])>,
		D: IntoIterator<Item=&'a &'b [u8]>,
	>(&self, insert: I, delete: D) -> error::Result<()> {
		// Import is locked here because we may have other block import
		// operations that tries to set aux data. Note that for consensus
		// layer, one can always use atomic operations to make sure
		// import is only locked once.
		self.lock_import_and_run(|operation| {
			self.apply_aux(operation, insert, delete)
		})
	}
	/// Query auxiliary data from key-value store.
	fn get_aux(&self, key: &[u8]) -> error::Result<Option<Vec<u8>>> {
		crate::backend::AuxStore::get_aux(&*self.backend, key)
	}
}
#[cfg(test)]
pub(crate) mod tests {
	use std::collections::HashMap;
	use super::*;
	use keyring::Keyring;
	use primitives::twox_128;
	use runtime_primitives::traits::DigestItem as DigestItemT;
	use runtime_primitives::generic::DigestItem;
	use test_client::{self, TestClient};
	use consensus::BlockOrigin;
	use test_client::client::{backend::Backend as TestBackend, runtime_api::ApiExt};
	use test_client::BlockBuilderExt;
	use test_client::runtime::{self, Block, Transfer, RuntimeApi, TestAPI};

	/// 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, RuntimeApi>,
		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.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.runtime_api().balance_of(
				&BlockId::Number(client.info().unwrap().chain.best_number),
				Keyring::Alice.to_raw_public().into()
			).unwrap(),
			1000
		);
		assert_eq!(
			client.runtime_api().balance_of(
				&BlockId::Number(client.info().unwrap().chain.best_number),
				Keyring::Ferdie.to_raw_public().into()
			).unwrap(),
			0
		);
	}

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

		assert!(
			client.runtime_api().has_api::<TestAPI<Block>>(
				&BlockId::Number(client.info().unwrap().chain.best_number),
			).unwrap()
		);
	}

	#[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.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.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.runtime_api().balance_of(
				&BlockId::Number(client.info().unwrap().chain.best_number),
				Keyring::Alice.to_raw_public().into()
			).unwrap(),
			958
		);
		assert_eq!(
			client.runtime_api().balance_of(
				&BlockId::Number(client.info().unwrap().chain.best_number),
				Keyring::Ferdie.to_raw_public().into()
			).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.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.import(BlockOrigin::Own, a1.clone()).unwrap();

		// A1 -> A2
		let a2 = client.new_block().unwrap().bake().unwrap();
		client.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.import(BlockOrigin::Own, a1.clone()).unwrap();

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

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

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

		// A4 -> A5
		let a5 = client.new_block_at(&BlockId::Hash(a4.hash())).unwrap().bake().unwrap();
		client.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.import(BlockOrigin::Own, b2.clone()).unwrap();

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

		// B3 -> B4
		let b4 = client.new_block_at(&BlockId::Hash(b3.hash())).unwrap().bake().unwrap();
		client.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.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.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 best_containing_with_max_depth_higher_than_best() {
		// block tree:
		// G -> A1 -> A2

		let client = test_client::new();

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

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

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

		assert_eq!(a2.hash(), client.best_containing(genesis_hash, Some(10)).unwrap().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 end = client.block_hash(end).unwrap().unwrap();
			let actual_result = client.key_changes(begin, BlockId::Hash(end), &StorageKey(key)).unwrap();
			match actual_result == expected_result {
				true => (),
				false => panic!(format!("Failed test {}: actual = {:?}, expected = {:?}",
					index, actual_result, expected_result)),
			}
		}
	}

	#[test]
	fn import_with_justification() {
		use test_client::blockchain::Backend;

		let client = test_client::new();

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

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

		// A2 -> A3
		let justification = vec![1, 2, 3];
		let a3 = client.new_block_at(&BlockId::Hash(a2.hash())).unwrap().bake().unwrap();
		client.import_justified(BlockOrigin::Own, a3.clone(), justification.clone()).unwrap();

		assert_eq!(
			client.backend().blockchain().last_finalized().unwrap(),
			a3.hash(),
		);

		assert_eq!(
			client.backend().blockchain().justification(BlockId::Hash(a3.hash())).unwrap(),
			Some(justification),
		);

		assert_eq!(
			client.backend().blockchain().justification(BlockId::Hash(a1.hash())).unwrap(),
			None,
		);

		assert_eq!(
			client.backend().blockchain().justification(BlockId::Hash(a2.hash())).unwrap(),
			None,
		);
	}
}