public async Task Get_BlockHash_ByHeight_ReturnNull()
        {
            var chain = await _fullBlockchainService.GetChainAsync();

            var result =
                await _fullBlockchainService.GetBlockHashByHeightAsync(chain, 14, chain.BestChainHash);

            result.ShouldBeNull();

            result = await _fullBlockchainService.GetBlockHashByHeightAsync(chain, 20, chain.LongestChainHash);

            result.ShouldBeNull();

            result = await _fullBlockchainService.GetBlockHashByHeightAsync(chain, 14,
                                                                            _kernelTestHelper.ForkBranchBlockList.Last().GetHash());

            result.ShouldBeNull();

            result = await _fullBlockchainService.GetBlockHashByHeightAsync(chain, 15,
                                                                            _kernelTestHelper.NotLinkedBlockList.Last().GetHash());

            result.ShouldBeNull();

            result = await _fullBlockchainService.GetBlockHashByHeightAsync(chain, 8,
                                                                            _kernelTestHelper.NotLinkedBlockList.Last().GetHash());

            result.ShouldBeNull();
        }