This DEV-only field was added in 836331ba5f69f2cc53b273ec073fae116db14302 by @sebmarkbage but it's not being used anymore to my knowledge.
return <div />;
    }
    const comp = ReactTestUtils.renderIntoDocument(<Child />);
    expect(comp).toBe(null);
  });
  it('should use correct name in key warning', () => {
    function Child() {
      return <div>{[<span />]}</div>;
    }
    expect(() => ReactTestUtils.renderIntoDocument(<Child />)).toErrorDev(
      'Each child in a list should have a unique "key" prop.\n\n' +
        'Check the render method of `Child`.',
    );
  });
  
  
  it('should support default props and prop types', () => {
    function Child(props) {
      return <div>{props.test}</div>;
    }
    Child.defaultProps = {test: 2};
    Child.propTypes = {test: PropTypes.string};
    expect(() => ReactTestUtils.renderIntoDocument(<Child />)).toErrorDev(
      'Warning: Failed prop type: Invalid prop `test` of type `number` ' +
        'supplied to `Child`, expected `string`.\n' +
        '    in Child (at **)',
    );
  });
  it('should receive context', () => {
    class Parent extends React.Component {