`p.isValid` is overridden here to force validation. I took this from the test just before it. As for the `if (done) { ... }`, I assumed it was being passed a callback on `save` since that's how it was overridden in the previous test. However it's called synchronously within the test to test it is _not_ valid both before `p.save` and on callback.

If `p.save` does not call `isValid` with a callback then I'll remove the `if (done) { ... }` (lines 170-172).