It is a Jest-ism that shouldn't be in our open source package.
People using Jest can implement a similar pattern directly.
const log = [];
    ReactTestUtils.findAllInRenderedTree(tree, function(child) {
      if (ReactTestUtils.isDOMComponent(child)) {
        log.push(ReactDOM.findDOMNode(child).textContent);
      }
    });
    
    expect(log).toEqual(['orangepurple', 'orange', 'purple']);
  });
  it('should support injected wrapper components as DOM components', () => {
    const injectedDOMComponents = [
      'button',
      'form',
      'iframe',
      'img',
      'input',
      'option',
      'select',
      'textarea',
    ];
    injectedDOMComponents.forEach(function(type) {
      const testComponent = ReactTestUtils.renderIntoDocument(
        React.createElement(type),
      );
      expect(testComponent.tagName).toBe(type.toUpperCase());
      expect(ReactTestUtils.isDOMComponent(testComponent)).toBe(true);
    });
    
    
    class Root extends React.Component {