如何在实际依赖项上提升一个笑话依赖项模拟？

Question

我正在测试一个导入类 LanguageStore 的 react-native 组件。目前测试失败，因为组件正在实例化这个类，该类调用了一个在测试范围内未定义的私有设置器：

FAIL  src\modules\languageProvider\__tests__\LanguageProvider-test.js
  ● renders correctly

    TypeError: _this.strings.setLanguage is not a function

      at LanguageStore.setLanguage (src\modules\languageProvider\LanguageStore.js:25:15)
      at new LanguageProvider (src\modules\languageProvider\LanguageProvider.js:30:16)

问题：

如何在实际依赖中提升一个玩笑的依赖模拟？

为了解决这个问题，我根据这个答案How can I mock an ES6 module import using Jest? 调用了jest.mock。但是我得到了和以前一样的错误，因为测试调用的是 LanguageStore 的实现，而不是我在下面创建的模拟 - _this.strings.setLanguage is not a function：

import { View } from 'react-native';
import React from 'react';
import { shallow } from 'enzyme';
import renderer from 'react-test-renderer';
import connect from '../connect.js';
import LanguageProvider from '../LanguageProvider';
import LanguageStore from '../LanguageStore';

it('renders correctly', () => {

  const TestComponent = connect(Test);
  const strings = { test: 'Test' };
  const language = "en"

  const stringsMock = {
    setLanguage: jest.fn()
  };

  const mockSetLanguage = jest.fn();
  jest.mock('../LanguageStore', () => () => ({
    language: language,
    strings: stringsMock,
    setLanguage: mockSetLanguage,
  }));

  const wrapper = shallow(<LanguageProvider strings={strings} language="en"><Test /></LanguageProvider>);

  expect(wrapper.get(0)).toMatchSnapshot();

});


class Test extends React.Component {
  constructor(props) {
    super(props);
  }
  render() {
    return <View />;
  }
}

这是一个链接到测试和相关的被测组件和类：

https://github.com/BrianJVarley/react-native-prototyping/blob/i18nProvider-feature/src/modules/languageProvider/tests/LanguageProvider-test.js

Answer 1

Calling jest.mock within a test doesn't work.

您需要将模拟移出测试并确保您的工厂函数没有任何外部依赖项。

类似这样的：

import { View } from 'react-native';
import React from 'react';
import { shallow } from 'enzyme';
import connect from '../connect.js';
import LanguageProvider from '../LanguageProvider';
import LanguageStore from '../LanguageStore';

jest.mock('../LanguageStore', () => {
  const language = "en"
  const stringsMock = {
    setLanguage: jest.fn()
  };
  const mockSetLanguage = jest.fn();

  return () => ({
    language,
    strings: stringsMock,
    setLanguage: mockSetLanguage,
  })
});

it('renders correctly', () => {
  const TestComponent = connect(Test);
  const strings = { test: 'Test' };
  const wrapper = shallow(<LanguageProvider strings={strings} language="en"><Test /></LanguageProvider>);
  expect(wrapper.get(0)).toMatchSnapshot();
});


class Test extends React.Component {
  constructor(props) {
    super(props);
  }
  render() {
    return <View />;
  }
}