用Jest部分模拟React模块

Question

我试图在导入的React模块中仅模拟一个功能，保持模块的其余部分不变，并在所有测试的顶层执行此操作。

我正在使用带有单个测试的新鲜create-react-app项目来观察问题。

重现步骤：

• create-react-app test
• 使用提供的src/App.test.js作为唯一的测试文件
• npm run test

App.test.js

jest.mock('react', () => {
  jest.dontMock('react');

  const React = require('react');
  const lazy = jest.fn();

  return {
    ...React,
    lazy
  };
});

import * as React from 'react';
const React2 = require('react');

it('should partially mock React module', async () => {
  expect(jest.isMockFunction(React.lazy)).toBe(true); // passes
  expect(jest.isMockFunction(React2.lazy)).toBe(true); // fails
  expect(jest.isMockFunction(require('react').lazy)).toBe(true); // fails
  expect(jest.isMockFunction((await import('react')).lazy)).toBe(true); // fails
});

这里的问题似乎是jest.dontMock因为它阻止了对require和动态import模拟，但是仍不清楚为什么可以使用这种方式模拟静态import ，因为它使用了require方式。 这是转档文件：

"use strict";

jest.mock('react', () => {
  jest.dontMock('react');

  const React = require('react');

  const lazy = jest.fn();
  return (0, _objectSpread2.default)({}, React, {
    lazy
  });
});

var _interopRequireWildcard3 = require("...\\node_modules\\@babel\\runtime/helpers/interopRequireWildcard");

var _interopRequireDefault = require("...\\node_modules\\@babel\\runtime/helpers/interopRequireDefault");

var _interopRequireWildcard2 = _interopRequireDefault(require("...\\node_modules\\@babel\\runtime/helpers/interopRequireWildcard"));

var _objectSpread2 = _interopRequireDefault(require("...\\node_modules\\@babel\\runtime/helpers/objectSpread"));

var React = _interopRequireWildcard3(require("react"));

const React2 = require('react');
...

这可能与create-react-app Jest + Babel设置有关，因为我无法使jest.dontMock无法与jest.dontMock Jest jest.dontMock正常工作并require 。

为什么React2静态的React导入但不React2 ？ 里面到底发生了什么？

如何固定jest.dontMock当前行为以在顶层部分模拟模块？

Answer 1

默认导入：

一个简单的解决方案是在React.lazy中模拟setupTest.js ：

import React from 'react';
import { configure } from 'enzyme';
import Adapter from 'enzyme-adapter-react-16';
configure({ adapter: new Adapter() });

jest.spyOn(React.lazy);

对于每个测试文件，将部分模拟任何随后的react require/imports 。

工作示例 ： https : //github.com/mattcarlotta/react-lazy-mocked （我不使用create-react-app ，但是可以按照我的设置方法来设置jest ）

安装：

• git clone git@github.com:mattcarlotta/react-lazy-mocked.git
• cd react-lazy-mocked
• yarn install
• yarn test

---

root / __ tests __ / root.test.js

import React from 'react';
import App from '../index.js';

const React2 = require('react');

describe('App', () => {
  const wrapper = mount(<App />);

  it('renders without errors', () => {
    const homeComponent = wrapper.find('.app');
    expect(homeComponent).toHaveLength(1);
  });

  it('should partially mock React module', async () => {
    expect(jest.isMockFunction(await require('react').lazy)).toBe(true); // eslint-disable-line global-require
    expect(jest.isMockFunction(React)).toBe(false);
    expect(jest.isMockFunction(React.lazy)).toBe(true);
    expect(jest.isMockFunction(React2)).toBe(false);
    expect(jest.isMockFunction(React2.lazy)).toBe(true);
  });

  it('should no longer be partially mocked within the test file', () => {
    React.lazy.mockRestore();
    expect(jest.isMockFunction(React.lazy)).toBe(false);
  });
});

pages / Home / __ tests __ / Home.test.js

import React from 'react';
import Home from '../index.js';

describe('Home', () => {
  const wrapper = shallow(<Home />);

  it('renders without errors', () => {
    const homeComponent = wrapper.find('.app');
    expect(homeComponent).toHaveLength(1);
  });

  it('should partially mock React module', async () => {
    expect(jest.isMockFunction(React.lazy)).toBe(true);
  });
});

---

命名进口：

工作示例 ： https : //github.com/mattcarlotta/named-react-lazy-mocked

安装：

• git clone git@github.com:mattcarlotta/named-react-lazy-mocked.git
• cd named-react-lazy-mocked
• yarn install
• yarn test

utils / __ mocks __ / react.js

jest.mock('react', () => ({
  ...require.requireActual('react'),
  lazy: jest.fn(),
}));
module.exports = require.requireMock('react');

utils / setup / setupTest.js （可选，您可以将模拟的react文件添加为global jest函数，这样就不必为每个测试都将import * as React from 'react'编写为import * as React from 'react' ）：

import { JSDOM } from 'jsdom';
import { configure } from 'enzyme';
import Adapter from 'enzyme-adapter-react-16';
// import React from '../__mocks__/react';

configure({ adapter: new Adapter() });

// global.React = React;

root / __ tests __ / root.test.js

import * as React from 'react';
import App from '../index.js';

const React2 = require('react');

describe('App', () => {
  const wrapper = mount(<App />);

  it('renders without errors', () => {
    const homeComponent = wrapper.find('.app');
    expect(homeComponent).toHaveLength(1);
  });

  it('should partially mock React module', async () => {
    expect(jest.isMockFunction(await require('react').lazy)).toBe(true); // eslint-disable-line global-require
    expect(jest.isMockFunction(React)).toBe(false);
    expect(jest.isMockFunction(React.lazy)).toBe(true);
    expect(jest.isMockFunction(React2)).toBe(false);
    expect(jest.isMockFunction(React2.lazy)).toBe(true);
  });
});