Programmatically adding and removing log appenders in log4net

Question

I have a component that uses log4net. I want to create unit tests, that validate that certain error conditions result in the correct logging.

I was thinking that the best way to do this is to create an ILogAppender implementation, for example a mock. I would then add the log appender to log4net during test setup, inspect what was written during test validation, and remove it again during test teardown.

Is this possible?

Answer 1

Using the BasicConfigurator is fine for unit testing (what the OP asked for, but not what's in the subject line). The other answers grab output for a specific logger.

I wanted it all (this was a 'self test' page within a website). In the end I did basically the following:

var root = ((log4net.Repository.Hierarchy.Hierarchy)LogManager.GetRepository()).Root; var attachable = root as IAppenderAttachable;  var appender = new log4net.Appender.MemoryAppender(); if(attachable!=null)     attachable.AddAppender(appender); // do stuff var loggingEvents = appender.GetEvents(); foreach (var loggingEvent in loggingEvents)     loggingEvent.WriteRenderedMessage(writer); if(attachable!=null)     attachable.RemoveAppender(appender); 

...but wrapped up as a Disposable as per @Pawel's approach

UPDATE: Pawel's answer was deleted, so I am adding his link here: Programmatically check Log4Net log.

Answer 2

I have been using the BasicConfigurator configured with a MemoryAppender. This appender lets you get to the in-memory messages logged during your test.