Function verifyTimeline

packages/core/test/acceptance/defer_spec.ts:104–145

* Allows to verify behavior of defer blocks by providing a set of * [time, expected output] pairs. Also allows to provide a function * instead of an expected output string, in which case the function * is invoked at a specified time.

(
  fixture: ComponentFixture<unknown>,
  ...slots: Array<[time: number, expected: string | VoidFunction]>
)

 * is invoked at a specified time.
 */
async function verifyTimeline(
  fixture: ComponentFixture<unknown>,
  ...slots: Array<[time: number, expected: string | VoidFunction]>
) {
  let actualTime = 0;
  for (let i = 0; i < slots.length; i++) {
    const targetVirtualTime = slots[i][0];
    const slotValue = slots[i][1];

    if (typeof slotValue === 'function') {
      const waitTime = Math.max(0, targetVirtualTime - actualTime);
      if (waitTime > 0) {
        await timeout(waitTime);
        actualTime += waitTime;
      }
      slotValue();
    } else {
      const waitTime = Math.max(0, targetVirtualTime - actualTime);
      if (waitTime > 0) {
        await timeout(waitTime);
        actualTime += waitTime;
      }

      let actual = '';
      let waited = 0;
      const maxWait = 40; // max ms to poll for the expected state

      while (waited <= maxWait) {
        fixture.detectChanges();
        actual = fixture.nativeElement.textContent.trim();
        if (actual === slotValue) {
          break;
        }
        await timeout(1);
        waited += 1;
        actualTime += 1;
      }

      expect(actual).withContext(`${targetVirtualTime}ms (actual ${actualTime}ms)`).toBe(slotValue);
    }
  }
}

class FakeTimerScheduler {
  cbs: VoidFunction[] = [];