Mocking 简单内部 function 使用 Jest 用于渲染的 React 组件

Question

I have a simple React application with the following App.js , App.test.js , and utils.js files:我有一个简单的 React 应用程序，其中包含以下App.js 、 App.test.js和utils.js文件：

App.js应用程序.js

import React from 'react';
import { randomNameGenerator } from './utils.js';
import './App.css';

function App() {
  return (
    <div>
      {randomNameGenerator()}
    </div>
  );
}

export default App;

App.test.js应用程序.test.js

import React from 'react';
import { render } from '@testing-library/react';
import '@testing-library/jest-dom/extend-expect'
import App from './App';

it('allows Jest method mocking', () => {
  const { getByText } = render(<App />);
  expect(getByText("Craig")).toBeInTheDocument()
});

utils.js实用程序.js

export function randomNameGenerator() {
    return Math.floor((Math.random() * 2) + 1) == 1 ? 'Steve' : 'Bill';
}

This is a simple example, but what I'm trying to accomplish is a Jest mock of the randomNameGenerator() function to only return "Craig" for that specific Jest test .这是一个简单的例子，但我想要完成的是randomNameGenerator() function 的 Jest 模拟，只为特定的 Jest test返回"Craig" 。

I've followed a wide variety of tutorials/guides, but can't find anything that works - the closest (by "feel") that I've gotten was this (in App.test.js ), which had no effect:我遵循了各种各样的教程/指南，但找不到任何有用的东西——我得到的最接近的（通过“感觉”）是这个（在App.test.js中），它没有任何效果：

jest.doMock('./utils', () => {
  const originalUtils = jest.requireActual('./utils');
  return {
    __esModule: true,
    ...originalUtils,
    randomNameGenerator: jest.fn(() => {
      console.log('## Returning mocked typing duration!');
      return 'Craig';
    }),
  };
})

The way it fails is expected:它失败的方式是预期的：

Unable to find an element with the text: Craig. This could be because the text is broken up by multiple elements. In this case, you can provide a function for your text matcher to make your matcher more flexible.

    <body>
      <div>
        <div>
          Steve
        </div>
      </div>
    </body>

       6 | it('allows Jest method mocking', () => {
       7 |   const { getByText } = render(<App />);
    >  8 |   expect(getByText("Craig")).toBeInTheDocument()
         |          ^
       9 | });

Answer 1

You can mock the module by calling jest.mock , and then import it, then inside your tests you call mockImplementation to setup the right return value.您可以通过调用jest.mock来模拟模块，然后导入它，然后在您的测试中调用mockImplementation来设置正确的返回值。

import React from 'react';
import { render } from '@testing-library/react';
import '@testing-library/jest-dom/extend-expect'
import App from './App';

import { randomNameGenerator } from "./utils";

jest.mock('./utils.js', () => ({ 
  randomNameGenerator: jest.fn()
}));

describe('test', () => {
  it('allows Jest method mocking 1', () => {
    randomNameGenerator.mockImplementation(() => "Craig");
    const { getByText } = render(<App />);
    expect(getByText("Craig")).toBeInTheDocument()
  });

  it('allows Jest method mocking 2', () => {
    randomNameGenerator.mockImplementation(() => "Not Craig");
    const { getByText } = render(<App />);
    expect(getByText("Not Craig")).toBeInTheDocument()
  });
});

Mocking 简单内部 function 使用 Jest 用于渲染的 React 组件

问题描述

1 个解决方案

解决方案1
0 2019-10-02 21:11:49

Mocking 简单内部 function 使用 Jest 用于渲染的 React 组件

问题描述

1 个解决方案

解决方案1 0 2019-10-02 21:11:49

解决方案1
0 2019-10-02 21:11:49