如何使用 Typescript 将 jest.spyOn 与 React 函数组件一起使用

Question

我正在使用 Typescript 和钩子开发一个 React 应用程序，我正在尝试将 Enzyme 与 Jest 结合使用来测试功能组件。我无法使用 jest.spyOn 来测试我的组件中的方法。 jest.spyOn 方法无法正确解析并在悬停时显示以下消息

"Argument of type '"validateBeforeSave"' is not assignable to parameter of type '"context" | "setState" | "forceUpdate" | "render" | "componentDidMount" | "shouldComponentUpdate" | "componentWillUnmount" | "componentDidCatch" | "getSnapshotBeforeUpdate" | ... 6 more ... | "UNSAFE_componentWillUpdate"'.ts(2345)"

我试图将实例转换为 'Any' -

const instance = wrapper.instance() as any;

这当然忽略了编译时的问题，但随后测试抛出组件上不存在函数的运行时错误。

Cannot spy the validateBeforeSave property because it is not a function; undefined given instead

// Some function Component

const SomeComponent = (props: IMyComponentProps) => {
  const { classes } = props;

  // Component has state
  const [count, setCount] = useState(0);

  function validateBeforeSave(){

  }

  function handleClick() {
  validateBeforeSave();
  .
  .
  .
  }

  return (
   <div>
      <Button>
      className="saveBtn"
      onClick={handleClick}
      </Button>
    </div>
  );

  };

  // Unit test
  describe('SomeComponent' () => {
  it('validates model on button click', () => {
      const wrapper = mount(
        <MuiThemeProvider theme={theme}>
          <SomeComponent/>
        </MuiThemeProvider>,
      );
  const instance = wrapper.instance();
      const spy = jest.spyOn(instance, "validateBeforeSave");
  wrapper
        .find('.saveBtn')
        .at(0)
        .simulate('click');
      expect(spy).toHaveBeenCalledTimes(1);
    });
  }

我在这里错过了什么？ spyOn 如何与函数组件一起工作？

我使用 create-react-app 模板创建了应用程序，它具有测试包的这些依赖项

"devDependencies": {
    "ts-jest": "^23.10.3",
    "@types/jest": "24.0.9",
    "@types/enzyme": "^3.9.1",
    "@types/enzyme-adapter-react-16": "^1.0.2",
    "enzyme": "^3.9.0",
    "enzyme-adapter-react-16": "^1.11.2",
    "enzyme-to-json": "^3.3.5",
  }

Answer 1

您的 validateBeforeSave 函数在 SomeComponent 中声明，使其成为无法在外部访问的 closed/private 作用域函数。您可以将该函数作为道具传递，然后您可以创建间谍并将其作为道具值传递到您的测试中，并测试传递的道具函数（间谍）是否被调用

所以你会像这样修改你的函数：

// some validator function
function validateBeforeSave(){
  ...
}

// Some function Component

const SomeComponent = (props: IMyComponentProps) => {
  const { classes, validateBeforeSave } = props;

  // Component has state
  const [count, setCount] = useState(0);


  function handleClick() {
  validateBeforeSave();
  .
  .
  .
  }

  return (
   <div>
      <Button>
      className="saveBtn"
      onClick={handleClick}
      </Button>
    </div>
  );

};

并且在你的单元测试中，是这样的：

  // Unit test
  describe('SomeComponent' () => {
  it('validates model on button click', () => {
      const validateSpy = jest.fn();
      const wrapper = mount(
        <MuiThemeProvider theme={theme}>
          <SomeComponent validateSpy={validateSpy}/>
        </MuiThemeProvider>,
      );
      const instance = wrapper.instance();
      wrapper
        .find('.saveBtn')
        .at(0)
        .simulate('click');
      expect(validateSpy).toHaveBeenCalledTimes(1);
    });
  }

Answer 2

我也遇到了同样的问题 - 我喜欢下面的 -

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;

测试 -

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，断言它是否被调用

检查 -

Answer 3

我在使用 React 16.x.x 模拟回调 prop 方法时遇到了类似的问题，酶实例方法 returns null，你可以做的是直接传递 jest.fn() 作为 prop。

示例：

  it('should invoke callback with proper data upon checkbox click', () => {
    const spyCheckboxClick = jest.fn((id, item) => ({
      id,
      item,
    }))
    const component: any = enzyme.mount(
      <SectionColumn {...{
        ...mockProps,
        onCheckboxClick: spyCheckboxClick,
      }} />
    );
    expect(spyCheckboxClick).toHaveBeenCalledTimes(0);
    // perform click to checkbox
    const checkboxComponent = component.find('StyledCheckbox');
    const input = checkboxComponent.first().children();
    input.simulate('change');
    expect(spyCheckboxClick).toHaveBeenCalledTimes(1);
    expect(spyCheckboxClick()).toEqual(null)
 });

如何使用 Typescript 将 jest.spyOn 与 React 函数组件一起使用

How to use jest.spyOn with React function component using Typescript

typescript

reactjs

jestjs

enzyme

ts-jest