title: Simple React/Enzyme test failing over map issue
body: <p>I have a simple react component with a simple test. It is failing for some reason. Can someone take a look at this? </p>
  
  <p>Here is the component. </p>
  
  <pre><code>import React from 'react'; 
  import ToDoItem from '../ToDoItem/ToDoItem';
  
  export default class ToDos extends React.Component {
      render() {
  
          const toDoItems = this.props.items.map((item, key) =&gt; (
              &lt;ToDoItem item={item} key={key} /&gt;
          )); 
  
          return (
              &lt;section&gt; 
                  { toDoItems }   
              &lt;/section&gt;
          )
      }
  }
  </code></pre>
  
  <p>Not rocket science. Here is the test: </p>
  
  <pre><code>it('displays all ToDo items passed as props', () =&gt; {
      const items = ['example1', 'example2']; 
      const toDos = mount(&lt;ToDos items={items} /&gt;);
      expect(toDos.contains(&lt;ToDoItem /&gt;)).toEqual(true);   
  });
  </code></pre>
  
  <p>The test seems very bothered by "TypeError: Cannot read property 'map' of undefined" It can't seem to read the items props. Am I not passing the array properly in the test? I can't see what's wrong here. The code itself works fine. It's just the test... Help!</p>