Test isolation validation should include canceling active test waiters in ember-test-watiers

[scalvert]

The ember-test-waiters library will soon include an API to cancel all pending waiters. This is a similar concept to where we cancel timers if test isolation validation is triggered:

ember-qunit/addon-test-support/ember-qunit/test-isolation-validation.js

Lines 94 to 100 in c27964a

	.finally(() => {
	// canceling timers here isn't perfect, but is as good as we can do
	// to attempt to prevent future tests from failing due to this test's
	// leakage
	run.cancelTimers();
	return doFinish();

This will help ensure that we don't leak state from one test to another, potentially 'wedging' the test waiters and creating an inconsistent state.

[rwjblue]

I'm a bit on the fence here, while I agree that it might seem nice to have I do not think that we can actually cancel the async operation that the waiters are paused on. This means that while the waiters will not pause tests any more, you actually are in a broken state. Silently swallowing that seems extremely bad...

[scalvert]

Had a good chat with @rwjblue offline. We agreed that adding this API will likely result in leaks actually occurring, defeating the point of the waiters.

We discussed evaluating settled when a test starts, and if we're not in a settled state, fail hard then so we don't incorrectly signal test failures on successive tests.

[rwjblue]

@scalvert - Should we close then?