title: how to test component parameters in constructor with Jest and Enzyme
body: <p>I have a <code>TestContainer</code>:</p>
  
  <pre><code>class TestContainer extends Component {
    constructor(props) {
      super(props)
      this.myValue = 5;
    }
  }
  </code></pre>
  
  <p>and I am using Jest with Enzyme for my testing, I would like to test <code>myValue</code> is successfully set to 5 when <code>TestContainer</code> is rendered. My testing code:</p>
  
  <pre><code>describe("TestContainer tests", () =&gt; {
    const wrapper = shallow(&lt;TestContainer /&gt;);
  
    it("TestContainer should start", () =&gt; {
      expect(wrapper.exists()).toBe(true);
      // I dont know how to get the value of myValue.
    });
  });
  </code></pre>
  
  <p>Could anyone help please.</p>