https://github.com/facebook/react/blob/30b47103d4354d9187dc0f1fb804855a5208ca9f/packages/scheduler/src/Scheduler.js#L180-L185
expect(Scheduler).toFlushWithoutYielding();
  });
  it('top-level immediate callbacks fire in a subsequent task', () => {
    scheduleCallback(ImmediatePriority, () =>
      Scheduler.unstable_yieldValue('A'),
    );
    scheduleCallback(ImmediatePriority, () =>
      Scheduler.unstable_yieldValue('B'),
    );
    scheduleCallback(ImmediatePriority, () =>
      Scheduler.unstable_yieldValue('C'),
    );
    scheduleCallback(ImmediatePriority, () =>
      Scheduler.unstable_yieldValue('D'),
    );
    
    expect(Scheduler).toHaveYielded([]);
    
    expect(Scheduler).toFlushExpired(['A', 'B', 'C', 'D']);
  });
  it('nested immediate callbacks are added to the queue of immediate callbacks', () => {
    scheduleCallback(ImmediatePriority, () =>
      Scheduler.unstable_yieldValue('A'),
    );
    scheduleCallback(ImmediatePriority, () => {
      Scheduler.unstable_yieldValue('B');
      
      scheduleCallback(ImmediatePriority, () =>
        Scheduler.unstable_yieldValue('C'),
      );