使用jestjs时模拟sessionStorage

Question

好的,所以我有一个简单的例子React组件与sessionStorage交互:

//App.jsx    
var React = require('react/addons');

var App = React.createClass({
  handleSubmit: function (e) {
  },

  handleNameChange: function (e) {
    sessionStorage.setItem('name', e.target.value);
  },

  render: function () {
    return (
      <form>
      <input type='text' label='Name' onChange={this.handleNameChange}/>
      <button type='submit' label='Submit' onClick={this.handleSubmit}/>
      </form>
    );
  }
});

module.exports = App;

我用Jest写了这个测试...

//App-test.js
jest.dontMock('../App.jsx');
jest.setMock('sessionStorage', require('../__mocks__/sessionStorage.js'));
describe('App', function () {
  var React = require('react/addons');
  var sessionStorage = require('sessionStorage');
  var App = require('../App.jsx');
  var TestUtils = React.addons.TestUtils;

  var testapp = TestUtils.renderIntoDocument(
    <App />
  );
  var input = TestUtils.findRenderedDOMComponentWithTag(testapp, 'input');

  it('starts with empty value for name input', function () {
    expect(input.getDOMNode().textContent).toEqual('');
  });

  it('updates sessionStorage on input', function () {
    console.log(typeof sessionStorage);
    TestUtils.Simulate.change(input, {target: {value: 'Hello!'}});
    expect(sessionStorage.getItem('name')).toEqual('Hello!');
  });
});

我在最后一段代码片段中手动模拟了sessionStorage:

//sessionStorage.js
var sessionStorage = {
  storage: {},
  setItem: function (field, value) {
    this.storage.field = value;
  },
  getItem: function (field) {
    return this.storage.field;
  }
};
module.exports = sessionStorage;

问题是,当我尝试运行测试时,它仍然抱怨sessionStorage未定义.即使在测试结束时调用console.log也会确认它已被定义,但错误会立即抛出到该行上.我在这里错过了什么？您可以从此处克隆整个项目以查看目录结构等.

Answer 1

为了在所有测试用例中解决这个问题,我使用了这个:

npm install mock-local-storage --save-dev

然后在你,在jest配置下的package.json:

  ...
  "jest": {
    ...
    "setupTestFrameworkScriptFile": "mock-local-storage"
  }
  ...

这将为所有测试用例添加模拟的localStorage和sessionStorage,您不需要在每个文件中进行更改.您也可以将代码放在文件中,并在setupTestFrameworkScriptFile下指定文件位置,而不是使用npm包.

您的代码应类似于:https://github.com/letsrock-today/mock-local-storage/blob/master/src/mock-localstorage.js

Answer 2

我也没有注入sessionStorage。我能够在beforeEach函数上模拟全局变量：

 beforeEach(function() {
       ...
       global.sessionStorage = jest.genMockFunction();
       global.sessionStorage.setItem = jest.genMockFunction();
       global.sessionStorage.getItem = jest.genMockFunction();
       ...
     }