This DEV-only field was added in 836331ba5f69f2cc53b273ec073fae116db14302 by @sebmarkbage but it's not being used anymore to my knowledge.
return {test: this.props.test};
      }
      render() {
        return <Parent />;
      }
    }
    const el = document.createElement('div');
    ReactDOM.render(<GrandParent test="test" />, el);
    expect(el.textContent).toBe('test');
    ReactDOM.render(<GrandParent test="mest" />, el);
    expect(el.textContent).toBe('mest');
  });
  it('should warn for getDerivedStateFromProps on a function component', () => {
    function FunctionComponentWithChildContext() {
      return null;
    }
    FunctionComponentWithChildContext.getDerivedStateFromProps = function() {};
    const container = document.createElement('div');
    expect(() =>
      ReactDOM.render(<FunctionComponentWithChildContext />, container),
    ).toErrorDev(
      'FunctionComponentWithChildContext: Function ' +
        'components do not support getDerivedStateFromProps.',
    );
  });
  it('should warn for childContextTypes on a function component', () => {
    function FunctionComponentWithChildContext(props) {