title: jest - mockReturnValue : Promise<boolean>
body: <p>I am new and I want to mock a function that returns a <code>Promise&lt;boolean&gt;.</code>
  I did this:</p>
  
  <pre><code>service.changeBookingAsync = jest.fn().mockReturnValue(boolean);
  </code></pre>
  
  <p>but I got this error :</p>
  
  <blockquote>
    <p>error TS2693: 'boolean' only refers to a type, but is being used as a
    value here.</p>
  </blockquote>