It is a Jest-ism that shouldn't be in our open source package.
People using Jest can implement a similar pattern directly.
render() {
        return (
          <div>
            <Stateless />
            <hr />
          </div>
        );
      }
    }
    const inst = ReactTestUtils.renderIntoDocument(<SomeComponent />);
    const hrs = ReactTestUtils.scryRenderedDOMComponentsWithTag(inst, 'hr');
    expect(hrs.length).toBe(2);
  });
  describe('Simulate', () => {
    it('should change the value of an input field', () => {
      const obj = {
        handler: function(e) {
          e.persist();
        },
      };
      spyOnDevAndProd(obj, 'handler').and.callThrough();
      const container = document.createElement('div');
      const node = ReactDOM.render(
        <input type="text" onChange={obj.handler} />,