public async Task Async_Error_Log_Call_Shoould_Write_File_Expected_Message__And_Path() { string message = LoggerProvider.CreateLogMessage(MessageLength.Normal); string expectedMessage = $"{_dateTimeProviderMock.UtcNow} [ERROR] {message}"; using (var stream = _streamFactoryMock.Create()) { var streamLogger = new StreamLogger(stream, _dateTimeProviderMock, _streamWriterMock); await streamLogger.LogAsync(LogLevel.Error, message); await _streamWriterMock.Received().WriteLineAsync(Arg.Any <Stream>(), Arg.Is(expectedMessage)); } }