1. override
Future<Null> pump([Duration duration, EnginePhase phase = EnginePhase.sendSemanticsTree ])

Triggers a frame after duration amount of time.

This makes the framework act as if the application had janked (missed frames) for duration amount of time, and then received a v-sync signal to paint the application.

This is a convenience function that just calls TestWidgetsFlutterBinding.pump.

Source 

@override
Future<Null> pump([
  Duration duration,
  EnginePhase phase = EnginePhase.sendSemanticsTree
]) {
  return TestAsyncUtils.guard(() => binding.pump(duration, phase));
}