how to write integration tests

There doesn't seem to be a guide about either testing or integration testing. It would be nice to see two guides:

plain vanilla junit tests:
how to write a simple one that will run in m2
how to write one that uses the test suite API

integration testing:
test building e.g. plugin that does code generation
test resulting application e.g. command-line app or gui
test deployment e.g. to a test web service container

I have no idea what of this is currently implemented or even possible using mvn, but then the documentation isn't giving my wishes any boundaries either...