Instead of testing that `backboneSync` gets called with `storeExists` in the options (which happens to be *how* we accomplish the goal), instead only assert that the actual goal is accomplished: the error callback is called. `ready` is only set to true if the error callback is called, so just the fact that `waitsFor (-> ready)` doesn't fail is good enough. The following `runs ->` function can be removed.

In other tests where I was trying to ensure that backboneSync gets called, I do make these assertions, because that's the goal of the test.