public void Append_BuffersMessageToBeSent() { var formatterMock = new Mock <ILogglyFormatter>(); formatterMock.Setup(x => x.ToJson(It.IsAny <LoggingEvent>(), It.IsAny <string>())) .Returns <LoggingEvent, string>((e, m) => $"Formatted: {e.RenderedMessage}"); var bufferMock = new Mock <ILogglyAsyncBuffer>(); var appender = new LogglyAppender(new Config(), formatterMock.Object, bufferMock.Object); var evt = new LoggingEvent(new LoggingEventData { Message = "test log" }); appender.DoAppend(evt); bufferMock.Verify(x => x.BufferForSend("Formatted: test log"), "message wasn't enqueued to be sent"); }