if (actContainerElement === null) {
      // warn if we can't actually create the stub element
      if (__DEV__) {
        warningWithoutStack(
          typeof document !== 'undefined' &&
            document !== null &&
            typeof document.createElement === 'function',
          'It looks like you called TestUtils.act(...) in a non-browser environment. ' +
            "If you're using TestRenderer for your tests, you should call " +
            'TestRenderer.act(...) instead of TestUtils.act(...).',
        );
      }
      // then make it
      actContainerElement = document.createElement('div');
    }
Pass a mocked component module to this method to augment it with
useful methods that allow it to be used as a dummy React component.
Instead of rendering as usual, the component will become a simple
<div> containing any provided children.

@param {object} module the mock function object exported from a
                       module that defines the component to be mocked
@param {?string} mockTagName optional dummy root tag name to return
                             from render method (overrides
                             module.mockTagName if provided)
@return {object} the ReactTestUtils object (for chaining)