UNSAFE_componentWillReceiveProps() {}
        render() {
          return null;
        }
      }
      expect(() => ReactTestRenderer.create(<SyncRoot />)).toWarnDev(
        'Unsafe lifecycle methods were found within a strict-mode tree:' +
          '\n    in SyncRoot (at **)' +
          '\n\ncomponentWillReceiveProps: Please update the following components ' +
          'to use static getDerivedStateFromProps instead: Bar, Foo' +
          '\n\nLearn more about this warning here:' +
          '\nhttps://fb.me/react-strict-mode-warnings',
      );
      
      const rendered = ReactTestRenderer.create(<SyncRoot />);
      rendered.update(<SyncRoot />);
    });
  });
  describe('symbol checks', () => {
    beforeEach(() => {
      jest.resetModules();
      React = require('react');
      ReactTestRenderer = require('react-test-renderer');
    });
    it('should switch from StrictMode to a Fragment and reset state', () => {
      const {Fragment, StrictMode} = React;
      function ParentComponent({useFragment}) {