title: act warning when testing component with Material UI Tooltip
body: <p>This is a follow up on <a href="https://github.com/mui-org/material-ui/issues/15726#issuecomment-507293766" rel="nofollow noreferrer">https://github.com/mui-org/material-ui/issues/15726#issuecomment-507293766</a></p>
  
  <p>I have a component <code>Registration</code> which has a button, that is by default is disabled (controlled by clicking a checkbox, accepting terms and conditions), and shows a tooltip message if hovered over,  to accept terms and conditions. Below is the result of the test, and the test itself.</p>
  
  <pre class="lang-js prettyprint-override"><code>√ without consent, cannot go further (190ms)
  
    console.error node_modules/react-dom/cjs/react-dom.development.js:506
      Warning: An update to ForwardRef(Popper) inside a test was not wrapped in act(...).        
      When testing, code that causes React state updates should be wrapped into act(...):
          act(() =&gt; {
        /* fire events that update state */
      });
      /* assert on the output */
          This ensures that you're testing the behavior the user would see in the browser. Learn more at ...
          in ForwardRef(Popper) (created by Tooltip)
          in Tooltip (created by WithStyles(Tooltip))
        ....
  </code></pre>
  
  <p>My test (using <code>@testing-library/react</code>):</p>
  
  <pre class="lang-js prettyprint-override"><code>
  jest.useFakeTimers()
  it('without consent, cannot go further', () =&gt; {
    const {getByText} = render(&lt;Registration/&gt;)
    const loginButton = getByText(/Log in/)
    act(() =&gt; {
      fireEvent.mouseEnter(loginButton)
      jest.runAllTimers()
    })
    expect(getByText(/Please accept our terms and conditions/)).toBeInTheDocument()
  })
  </code></pre>
  
  <p>I added fake timers as suggested on the GitHub issue, but it did not help.</p>