在0.57更新后,使用Typescript和Jest的React Native被破坏:无法找到相对于目录的预设"module:metro-react-native-babel-preset"

Question

如果您在新的React版本0.57和TypeScript中将测试与Jest和Enzyme集成,它们将无法工作.以下是重现的步骤:

创建一个新的React Native项目:

react-native init MyApp -package "com.my.app" --template typescript && node MyApp/setup.js

安装所有与Jest和Enzyne相关的包:

npm install --save-dev react-dom enzyme enzyme-react-adapter-16 jest-fetch-mock ts-jest

添加jest配置:

"jest": {
  "preset": "react-native",
  "moduleFileExtensions": [
    "ts",
    "tsx",
    "js"
  ],
  "transform": {
    "^.+\\.(js)$": "<rootDir>/node_modules/babel-jest",
    "\\.(ts|tsx)$": "<rootDir>/node_modules/ts-jest/preprocessor.js"
  },
  "testRegex": "(/__tests__/.*|\\.(test|spec))\\.(ts|tsx|js)$",
  "testPathIgnorePatterns": [
    "\\.snap$",
    "<rootDir>/node_modules/"
  ],
  "cacheDirectory": ".jest/cache",
  "setupFiles": [
    "./tests/setup.js"
  ]
}

添加文件tests/setup.js并包含以下配置:

import Enzyme from "enzyme";
import Adapter from "enzyme-adapter-react-16";
import { NativeModules } from "react-native";

global.fetch = require("jest-fetch-mock"); // eslint-disable-line no-undef
jest.mock("react-native-config");
Enzyme.configure({ adapter: new Adapter() });

最后但并非最不重要的是添加一个基本测试(App.test.tsx)来检查Jest和Enzyme是否有效:

import React from "react";
import { shallow } from "enzyme";
import { View } from "react-native";
import App from "./App";

const createTestProps = props => ({
  ...props
});

describe("App", () => {
  describe("rendering", () => {
    let wrapper;
    let props;
    beforeEach(() => {
      props = createTestProps({});
      wrapper = shallow(<App {...props} />);
    });

    it("should render a <View />", () => {
      expect(wrapper.find(View)).toHaveLength(1);
    });
  });
});

如果您现在尝试运行测试,则会收到以下错误消息:

 FAIL  app/App.test.tsx
  ? Test suite failed to run

    Couldn't find preset "module:metro-react-native-babel-preset" relative to directory "<Directory"

编辑

这似乎与Babel有关.

Answer 1

我在这个问题上找到了答案:https://github.com/facebook/metro/issues/242#issuecomment-421139247

基本上,将其添加到您的Jest部分package.json:

"transform": { "^.+\\.js$": "<rootDir>/node_modules/react-native/jest/preprocessor.js" }

Answer 2

在升级到0.57时有一个类似的问题,我package.json仍然包含一个条目babel-preset-react-native(现在已经弃用了它metro-react-native-babel-preset).我所要做的就是

yarn remove babel-preset-react-native

然后

yarn add metro-react-native-babel-preset --dev

最后,确保你改变.babelrc了

{
  "presets": ["react-native"]
}

至

{
  "presets": ["module:metro-react-native-babel-preset"]
}

更多信息可以在这里找到