reactjs - 用玩笑和 enzyme 从事React功能成分法的侦查；无法监视原始值

我正在尝试测试React组件，并确保在单击其按钮时，调用正确的方法。但是，当我尝试运行测试并尝试监视该方法时，收到以下消息：


  错误：无法对原始值进行spyOn；未给定


如何测试单击按钮时是否调用了正确的方法？谢谢！

sampleComponent.jsx：

import * as React from 'react';

const SampleComponent = () => {
  const sampleMethod = () => {
    console.log('hello world');
  };

  return <button onClick={sampleMethod} type="button">Click Me</button>;
};

export default SampleComponent;

sampleComponent.test.jsx：

import * as React from 'react';
import { shallow } from 'enzyme';
import SampleComponent from './sample';

test('testing spy', () => {
  const spy = jest.spyOn(SampleComponent.prototype, 'sampleMethod');
  const wrapper = shallow(<SampleComponent />);
  wrapper.find('button').simulate('click');
  expect(spy).toHaveBeenCalled();
});

最佳答案

该错误意味着，您在功能组件sampleMethod中定义的功能SampleComponent未在SampleComponent.prototype中定义。所以SampleComponent.prototype.sampleMethod是undefined，开玩笑不能窥探undefined值。

因此，测试sampleMethod事件处理程序的正确方法是这样的：

index.spec.tsx：

import React from 'react';
import SampleComponent from './';
import { shallow } from 'enzyme';

describe('SampleComponent', () => {
  test('should handle click correctly', () => {
    const logSpy = jest.spyOn(console, 'log');
    const wrapper = shallow(<SampleComponent></SampleComponent>);
    const button = wrapper.find('button');
    expect(button.text()).toBe('Click Me');
    button.simulate('click');
    expect(logSpy).toBeCalledWith('hello world');
  });
});

我们可以监视console.log，断言是否调用它。

单元测试结果覆盖率100％：

 PASS  src/react-enzyme-examples/02-react-hooks/index.spec.tsx
  SampleComponent
    ✓ should handle click correctly (19ms)

  console.log node_modules/jest-mock/build/index.js:860
    hello world

-----------|----------|----------|----------|----------|-------------------|
File       |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
-----------|----------|----------|----------|----------|-------------------|
All files  |      100 |      100 |      100 |      100 |                   |
 index.tsx |      100 |      100 |      100 |      100 |                   |
-----------|----------|----------|----------|----------|-------------------|
Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        5.036s

依赖版本：

"react": "^16.11.0",
"enzyme": "^3.10.0",
"enzyme-adapter-react-16": "^1.15.1",
"jest": "^24.9.0",
"jest-environment-enzyme": "^7.1.1",
"jest-enzyme": "^7.1.1",