If you're suspecting a problem in their code, I'd suggest setting up a bare minimum test case that demonstrates the flaw and posting it as a bug report (where you would do that, I'm not sure--I'm just getting my head around these libraries. Day two and counting.)
If you are trying to debug your own code moving through the JS API, you might want to consider using a Mocking library so you can see how your code is behaving under given hard-wired behavior you don't have to debug into.
Jasmine is a java testing framework that could help you outt in either case. Jasmine Spy is a mocking feature set, and JSMockito is another mocking library I've heard positive things about (but not yet gotten around to using unfortunately).
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