I moved it to test/unit/runtime/Loader.

Loader will call it's hooks.locate(), which in our case would be LoaderHooks.locate(), so that is where I choose to test it. 

Loader.locate() is valid, but it calls LoaderHooks.locate(). Once we have System as an instance of Loader, then System.locate() would work, but it would call LoaderHooks.locate() unless System has been changed. But we want to test our impl, ergo LoaderHooks.locate(). 

Does that make sense?