Initial project

一開始一定是先 initial project helloworld

  $ react-native init helloworld
  $ yarn test
  > helloword@0.0.1 test /Users/linweiqin/Projects/helloword
  > jest

  No tests found
  In /Users/linweiqin/Projects/helloword
    645 files checked.
    testMatch: **/__tests__/**/*.js?(x),**/?(*.)+(spec|test).js?(x) - 1 match
    testPathIgnorePatterns: /node_modules/ - 7 matches
  Pattern:  - 0 matches
  npm ERR! Test failed.  See above for more details.

因為我是使用 redux-saga

所以建一個測試

tests/saga.test.js

import { testSaga } from 'redux-saga-test-plan';
import { take, put, call} from "redux-saga/effects";

function identity(value) {
  return value;
}

function* mainSaga(x, y) {
  const action = yield take('HELLO');

  yield put({ type: 'ADD', payload: x + y });
  yield call(identity, action);
}

const action = { type: 'TEST' };

it('works with unit tests', () => {
  testSaga(mainSaga, 40, 2)
    // advance saga with `next()`
    .next()

    // assert that the saga yields `take` with `'HELLO'` as type
    .take('HELLO')

    // pass back in a value to a saga after it yields
    .next(action)

    // assert that the saga yields `put` with the expected action
    .put({ type: 'ADD', payload: 42 })

    .next()

    // assert that the saga yields a `call` to `identity` with
    // the `action` argument
    .call(identity, action)

    .next()

    // assert that the saga is finished
    .isDone();
});

  $ yarn add redux-saga
  $ yarn add -D redux-saga-test-plan
  $ yarn test

在 package.json 要加上一個設定

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

基本上這樣可以測試一般的

但是希望可以測試 Component

App.test.js

// __tests__/App.test.js
import React from 'react';
import App from '../App';

import renderer from 'react-test-renderer';

test('renders correctly', () => {
  const tree = renderer.create(<App />).toJSON();
  expect(tree).toMatchSnapshot();
});

React 與 React Native

如果使用同一個架構的話 React 與 React Native 是大同小異的

但是基於兩個的底層是完全不同的

一個是 Web HTML 一個是 Native code

希望使用盡量一致的 Lib 來做測試似乎困難度有點高

雖然尚未有完全無違和的測試

還是可以利用 Jest + Enzyme + Jsdom 來為 React Native 模擬 mount 環境

續前章 初步使用 Jest + Enzyme 做 React Native 測試

如果要在 測試中使用 mount 的話

會顯示 document is undefined 的錯誤

所以為了彌補這個問題

我們需要做一些補充

shallow and mount 的不同

shallow

shallow 針對 Component 做單一的單元測試，並不會直接顯示他的 Children Component

mount

mount 會完整的 render 所有的 Component 包含他下層的所有 Component

  import React from 'react';
  import App from '../App';
  import { mount, shallow } from 'enzyme';

  import renderer from 'react-test-renderer';

  test('renders correctly', () => {
    const tree = renderer.create(<App />).toJSON();
    expect(tree).toMatchSnapshot();
  });

  test('mount component', () => {
    const wrapper = shallow(<App />);
    
  });

會產生這個錯誤

因為找不到 global document

  $ yarn add enzyme jest-enzyme enzyme-adapter-react-16 enzyme-react-16-adapter-setup --dev

需要再 package.json 中增加

{
  ...,
  "jest": {
    "preset": "react-native",
    "setupTestFrameworkScriptFile": "./node_modules/jest-enzyme/lib/index.js",
    "setupFiles": [
      "enzyme-react-16-adapter-setup"
    ],
    "transform": {
      "^.+\\.js$": "<rootDir>/node_modules/react-native/jest/preprocessor.js"
    }
  }
}

缺少了 react-dom

  $ yarn add react-dom --dev

這時候就可以執行了

但是因為 shallow 只能 render 一層

如果要完整 render 的話要使用 mount

但是這樣會造成因為找不到 global document

要先增加 setupFile.js

  $ yarn add jsdom enzyme-adapter-react-16 react-native-mock-render --dev

const { JSDOM } = require('jsdom');

const jsdom = new JSDOM();
const { window } = jsdom;

function copyProps(src, target) {
  const props = Object.getOwnPropertyNames(src)
    .filter(prop => typeof target[prop] === 'undefined')
    .map(prop => Object.getOwnPropertyDescriptor(src, prop));
  Object.defineProperties(target, props);
}

global.window = window;
global.document = window.document;
global.navigator = {
  userAgent: 'node.js',
};
copyProps(window, global);

import Enzyme from "enzyme";
import Adapter from "enzyme-adapter-react-16";

Enzyme.configure({ adapter: new Adapter() });

// Ignore React Web errors when using React Native
console.error = (message) => {
  return message;
};

require('react-native-mock-render/mock');

  $ yarn remove enzyme-react-16-adapter-setup

package.json 也要做一些調整

{
  ...,
  "jest": {
    "preset": "react-native",
    "cacheDirectory": "./cache",
    "coveragePathIgnorePatterns": [
      "./app/utils/vendor"
    ],
    "coverageThreshold": {
      "global": {
        "statements": 80
      }
    },
    "transformIgnorePatterns": [
      "/node_modules/(?!react-native|react-clone-referenced-element|react-navigation)"
    ],
    "transform": {
      "^.+\\.js$": "<rootDir>/node_modules/react-native/jest/preprocessor.js"
    },
    "setupTestFrameworkScriptFile": "./setupFile.js"
  }
}