There are some tests that use FakeAsync.run() that are not awaiting the call, for example:

It seems like this is resulted in the tests always passing immediately. For example adding throw 'fail'; as the first line inside the callback does nothing - the test still passes.

I think these tests need await in front of the FakeAsync().run, however doing so right now causes them to hang - which I think is because the implementation uses await which queues a microtask but the queue is never flushed (since the code stops on the await).

Based on what @Hixie said, I think flutter_test is handling this by constantly pumping the microtask queue, however the flutter_tools tests don't run with flutter_test so don't have an equivilent. I think the relevant code in flutter_test is this bit:

cc @Hixie @jonahwilliams