So, I’m testing a method that uses both

suspendCancellableCoroutine {}

and

withTimeout {}

, and I’m running that test using a TestCoroutineDispatcher. In particular, I’m testing that the timeout fires if

cont.resume()

is never called within

suspendCancellableCoroutine {}

. My test runs the code in question inside a <test coroutine dispatcher>.runBlockingTest {} block. What I’m finding is that sometimes, the test passes as expected. But other times (it really feels nondeterministic and timing-related --- it changes depending on which tests are called before it, and whether or not it’s called in a debugger), instead of hitting the timeout, the internal call to

dispatcher.advanceUntilIdle()

leaves the test dispatcher idle but the coroutine still running, resulting in an IllegalStateException.