wip: use virtual time for timeout

[mightyguava]

Use virtual time instead of wall time for turbine timeout.

Proof of concept for discussion in #268. This PR should not be merged since it is non-backwards compatible. It should probably be an option instead.

I only ran tests against jvm.

[jingibus]

Adding these withContext(Default) calls here defeats the entire purpose of these tests.

In any of these tests that uses withContext(Default) within the test subject, the test subject is simulating the experience of an engineer whose code is broken.

If we also run awaitComplete() on the Default dispatcher, we're no longer simulating the experience of that engineer, becuase they won't be calling awaitComplete() on Default: they'll be calling it on TestScope's dispatcher.

This is a critical service that Turbine provides: unlike runTest's timeout, Turbine provides specific feedback on which expected output failed to emit.

[jingibus]

In any of these tests that uses withContext(Default) within the test subject, the test subject is simulating the experience of an engineer whose code is broken.

To clarify this: it simulates this because the engineer literally has a test that is hanging awaiting some value, and their wall clock is ticking.

To me, an interesting test for your change would be something like this:

@Test fun awaitFailsOnVirtualTime() = runTestTurbine {
  assertFailsWith<AssertionError> {
    flow<Nothing> {
      delay(1500.milliseconds)
    }.test(timeout = 1000.milliseconds) {
      awaitComplete()
    }
  }
}

Or:

@Test fun awaitFailsOnVirtualTime() = runTestTurbine {
  assertFailsWith<AssertionError> {
    flow<Nothing> {
      awaitCancellation()
    }.test {
      awaitComplete()
    }
  }
}

...in other words, can we just ditch the wallclock time stuff and rely entirely on virtual time?

[mightyguava]

Thanks! I really had no idea what the broken tests were for.

7ba8b1f adds both tests you suggested, both passing.

[mightyguava]

can we just ditch the wallclock time stuff and rely entirely on virtual time?

That would be really nice 😄 and also what I'm hoping for.