title: ui testing xcode, how to tap on a table view cell button with cellquery
body: <p>I am currently doing ui tests for my app and stuck on clicking on the log in button of my app. I am unable to find the element which i have gave the identifier signup button(the element is the 3rd by index, this is not the issue).</p>
  
  <pre><code>let cellQuery = self.app.tables.cells.element(boundBy: 3)
  
  let signInButton = cellQuery.buttons["signup button"]
  if signInButton.exists {
      signInButton.tap()
  }
  </code></pre>