DOM 操作

    displayUser.js

    __tests__/displayUser-test.js

    1. 'use strict';
    3. jest.mock('../fetchCurrentUser');
    5. test('displays a user after a click', () => {
    6.   // Set up our document body
    7.   document.body.innerHTML =
    8.     '<div>' +
    9.     '  <span id="username" />' +
    10.     '  <button id="button" />' +
    11.     '</div>';
    13.   require('../displayUser');
    15.   const $ = require('jquery');
    16.   const fetchCurrentUser = require('../fetchCurrentUser');
    18.   // Tell the fetchCurrentUser mock function to automatically invoke
    19.   // its callback with some data
    20.   fetchCurrentUser.mockImplementation(cb => {
    21.     cb({
    22.       fullName: 'Johnny Cash',
    23.     });
    26.   // Use jquery to emulate a click on our button
    27.   $('#button').click();
    29.   // Assert that the fetchCurrentUser function was called, and that the
    30.   // #username span's inner text was updated as we'd expect it to.
    31.   expect(fetchCurrentUser).toBeCalled();
    32.   expect($('#username').text()).toEqual('Johnny Cash - Logged In');
    33. });

    我们mock了 的实现，这样我们的测试就不会产生真正的网络请求，而是使用本地mock的数据。 这确保了我们的测试能够在毫秒级完成，而不是秒，并且保证了快速的单元测试迭代速度。