Test destroyable (?)

[MelSumner]

From #348

So I thought I suitable reproduced my error in #347 but it turns out the timing issue in my application was more subtle than that. We were still seeing the same issue, so the order of execution must be:
route change handler -> schedule afterRender -> component unrenders -> route handler removed -> afterRender runs w/o the element -> error about no element to focus()
This PR also cancels the schedule'd execution and we're no longer seeing the issue in our test suite. My issue though is this: I don't know how to recreate this situation in a test - any ideas or pointers?

[MelSumner]

I think this was already resolved?