resolvePending method
Completes every pending delay immediately, without advancing time.
For teardown: a test that finishes with delays outstanding would otherwise leave futures that never complete, which surfaces later as a confusing timeout in an unrelated test.
Implementation
Future<void> resolvePending() async {
final outstanding = List<_PendingDelay>.of(_pending);
_pending.clear();
for (final pending in outstanding) {
if (!pending.completer.isCompleted) pending.completer.complete();
}
await _drainMicrotasks();
}