Curently, the signature of TestContainerFactory.support() method is
<T extends AppDescriptor> Class<T> supports();
With such signature users will always have warnings when trying to implement method returning some subclass of AppDescriptor like LowLevelAppDescriptor.class . The reason is that it is impossible to implement the method correctly due to Java generics limitations. Any trial results in "rowtype" or "unchecked" warning.
The only thing current signature gives is a possibility to call the method like
TestContainerFactory tcf = ...
But this is not necessary, as the method is called only once from JerseyTest.getContainer() method like
Class<? extends AppDescriptor> adType = tcf.supports();
I suggest to change the signature to
Class<? extends AppDescriptor> supports();
This definitelly will not break anything(maybe, existing clients will need recompilation), and will help me and other users to avoid warnings.