PhantomJS 2.0 hanging on ember test

I have a straightforward ember-cli app. I run the unit tests with ember test, which runs them in phantomJS. A test using Function.prototype.bind is failing, because of the well-known issue of phantom 1.9.x missing that API. I installed phantom 2.0, but now when I run ember test, after successfully building, the tests never run and it simply sits there hanging, no error, nothing.

Any ideas about what the issue could be here, or how to track it down?

OS is Windows.