好的，我有一个简单的React组件示例，它与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。甚至在测试快结束时调用console.log也确认它已定义，但在紧接着的行中抛出错误。我在这里遗漏了什么？您可以从here克隆整个项目以查看目录结构等。