用于单元测试的触发事件 [英] Triggering event for unit testing

问题描述

我正在尝试使用在浏览器中运行的Mocha在我的单元测试中触发滚动事件。我有以下代码：

I am trying to trigger a scroll event inside of my unit test using Mocha running in a browser. I have the following code:

describe('Background Change', function() {
  describe('toogleBgHandler()', function() {
  it('should contain toggle-bg when scrollTop is more than 0', function() {
    let html = document.createElement('html');
    var target = [];
    target.push(html);
    let body = document.createElement('body');
    let div = document.createElement('div');
    html.appendChild(body);
    body.appendChild(div);
    document.body.dispatchEvent(new Event("scroll"));
    toggleBgHandler(target, div)
    chai.assert.isTrue(div.classList.contains("toggle-bg"));
  });
  });
});

我正在尝试测试的功能：

Function I am trying to test:

function toggleBgHandler(html, ele) {
        document.addEventListener("scroll", (e) => {
        if (html[0].scrollTop === 0) {
            ele.classList.remove("toggle-bg");
        } else {
            ele.classList.add("toggle-bg");
        }
      });
    }

如何为依赖它的函数触发滚动事件？我也尝试过创建一个事件对象，但这也不起作用。任何指针都会很棒。

How do I trigger a scroll event for a function that depends on it? I have also tried creating an event object, but that didn't work either. Any pointers would be great.

推荐答案

您的代码在窗口中寻找的滚动事件或者_元素？如果它在窗口上，你应该能够发送这样的滚动事件：

Is the scroll event your code is looking for on the window or on an _element? If it's on the window, you should be able to dispatch a scroll event like this:

window.dispatchEvent(new Event('scroll'));

否则，你可以这样做：

element.dispatchEvent(new Event('scroll'));

这是一个jsfiddle 演示。

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