Testing processor logging message in Junit tests

[DAVID SMITH]

Hi
Does anyone know how to test for logging messages generated by my processors in 
my Juint tests for that processor?I am trying to determine whilst testing my 
processor if I have entered an exception, where I would just normally log a 
warning or an Error but necessarily end up on the failure relationship.
Is there a good example of this anywhere within the current codebase?
Many thanksDave