title: React Testing library testing error `NaN` is an invalid value for the `left` css style property
body: <p>I am using internal library component that uses <a href="https://popper.js.org/react-popper/" rel="nofollow noreferrer">React popper</a>. Component is a dropdown that should open when i click on a marked element, as any other dropdown menu should.</p>
  <p>I am trying to test with React testing library flow where user opens dropdown and does some interaction. But when i make my test open that dropdown it throws this error (warning):</p>
  <pre><code>Warning: `NaN` is an invalid value for the `left` css style property.
   at div
          at Popover__MenuArrow (/my-project/node_modules/styled-components/src/models/Keyframes.js:20:51)
          at WithTheme(Component) (/my-project/node_modules/styled-components/src/models/ServerStyleSheet.js:66:13)
          at div
          at Popover__DropdownContainer (/my-project/node_modules/styled-components/src/models/Keyframes.js:20:51)
          at WithTheme(Component) (/my-project/node_modules/styled-components/src/models/ServerStyleSheet.js:66:13)
  ...
  </code></pre>
  <p>This is not a blocking error, it is a warning, and test actually passes, but it is annoying to see it all the time when i run my tests.</p>
  <p>My question is, how can I make this warning text not show when i run my tests?</p>
  <p>This is the test code:</p>
  <pre class="lang-js prettyprint-override"><code>it('Should open dropdown menu', () =&gt; {
    const { getByTestId } = render(&lt;DropdownMenu /&gt;);
  
    // Click on dropdown and open it
    const dropdownButton = getByTestId('my-dropdown-menu');
    fireEvent.click(dropdownButton);
  
    // Assert if dropdown list is visible
    const dropdownList = getByTestId('my-dropdown-list');
    expect(dropdownList).toBeTruthy();
  });
  </code></pre>