title: Parallel support using Jest with Puppeteer
body: <p>I am using puppeteer for UI automation along with Jest as a test runner. I am able to run tests sequentially but i am facing an issue when running tests in parallel.
  My page launch</p>
  
  <pre><code>beforeEach(async () =&gt; {
    browser = await puppeteer.launch({
      headless: false,
      //slowMo: 80,
      args: [`--window-size=${width},${height}`]
    });
    page = await browser.newPage();
    await page.setViewport({width, height});
  });
  
  // and my tests are
  test.concurrent("description", async () =&gt; {
    await page.goto('xxxx.com');
    //test code goes here
  }, timeout)
  test.concurrent("description ", async () =&gt; {
    //test code goes here
  }, timeout)
  </code></pre>
  
  <p>I am getting following error,   </p>
  
  <pre class="lang-none prettyprint-override"><code>TypeError: Cannot read property 'goto' of undefined
  (node:9552) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'addExpectationResult' of undefined
  (node:9552) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 3)
  (node:9552) [DEP0018] DeprecationWarning: Unhandled promise rejections are depre cated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
  npm ERR! Test failed.  See above for more details.
  </code></pre>
  
  <p>Any help in this regard would be appreciated.
  regards,
  Jay</p>