When running integration tests with logging configured, there is no logging output neither on the console, in configured file nor junit reports.
As I can understand, problem originates from _GrailsTest script, which first includes both _GrailsBootstrap (which includes _GrailsPackage), and after it, _GrailsWar. _GrailsPackage and _GrailsWar both have startLogging target, but the one in _GrailsWar does nothing since it is empty. Unfortunately, it overrides startLogging from _GrailsPackage. All this result with missing logging output.
There is a hacky workaround which will output logging statements to configured appenders, but not in junit reports. To enable it, modification of integrationTestPhasePreparation closure from _GrailsTest is needed. Basically, at the end of it, you can paste code from _GrailsPackage's startLogging target:
I'm not sure if this will mess up something else, but at least I've got logging working.