我想检查当在我的组件上单击按钮时，它会调用我创建的方法来处理单击。这是我的组件：

import React, { PropTypes, Component } from 'react';

class Search extends Component {

  constructor(){
    super();
    this.state = { inputValue: '' };
  }

  handleChange = (e) => {
    this.setState({ inputValue: e.target.value });
  }

  handleSubmit = (e) => {
    e.preventDefault();
    return this.state.inputValue;
  }

  getValue = () => {
    return this.state.inputValue;
  }

  render(){
    return (
      <form>
        <label htmlFor="search">Search stuff:</label>
        <input id="search" type="text" value={this.state.inputValue} onChange={this.handleChange} placeholder="Stuff" />
        <button onClick={this.handleSubmit}>Search</button>
      </form>
    );
  }
}

export default Search;

这是我的测试

  import React from 'react';
  import { mount, shallow } from 'enzyme';
  import Search from './index';
  import sinon from 'sinon';

  describe('Search button', () => {

    it('calls handleSubmit', () => {
      const shallowWrapper = shallow(<Search />);
      const stub = sinon.stub(shallowWrapper.instance(), 'handleSubmit');
      shallowWrapper.find('button').simulate('click', { preventDefault() {}     });
      stub.called.should.be.true();
    });

  });

名为 property 的调用返回 false。我已经尝试了大量的语法变化，我想也许我只是缺少一些基本的东西。任何帮助将不胜感激。