title: Jasmine.createSpy equivalent in jest
body: <p>I am migrating from jasmine to jest in my application. I have the following line to test</p>
  <pre><code>JSON.parse(window.document.querySelector(SELECTOR).innerHTML)
  </code></pre>
  <p>In my test I used jasmine.</p>
  <pre><code>document.querySelector = jasmine.createSpy('HTML Element').and.returnValue(dummyEl)
  </code></pre>
  <p>But now with jest I get the following error</p>
  <pre><code>TypeError: Cannot read property 'innerHTML' of null
  </code></pre>
  <p>Can you help me?</p>