Javascript 如何使用Jest单元测试触发transitionend

我使用angular 8和Jest进行单元测试。我已经在元素上添加了一个“transitionend”的侦听器，但是我还没有弄清楚如何使用Jest触发/模拟transitionend事件

this.animatedElement.nativeElement.addEventListener('transitionend', () => {
      this.transitionEnded = true;
});

---

我正在尝试创建一个单元测试来测试

这一点。transitionEnded

是真的

我能够找到一些适合我的东西

it('Should set transitionEnded to true', () => {
    // created 'transitionend' event
    const event = new Event('transitionend');
    const component = TextBed.createComponent(AppComponent).componentInstance;

    // call method that adds event listener to animatedElement
    component.methodToAddListener();
    // dispatch event that you created on animatedElement
    component.animatedElement.nativeElement.dispatchEvent(event);

    expect(component.transitionEnded).toBe(true);
});

---

使用此帮助器函数可触发任何事件：

function triggerTransitionEnd(element) {
   let event = document.createEvent("Event");
   event.initEvent("transitionend", true, true);
   element.dispatchEvent(event);
}

然后在测试中，像这样使用它：

test("Some description here", () => {
    const popup = document.getElementById("popup");
    triggerTransitionEnd(popup);
    expect(popup.classList.contains("show")).toBeFalsy();
});