*feature*

>Warning: A component is `contentEditable` and contains `children` managed by React. It is now your responsibility to guarantee that none of those nodes are unexpectedly modified or duplicated. This is probably not intentional.

It would help heaps if I would know _which_ component is causing this.
container,
      );
      
      ReactDOM.render(
        <div>
          <div key="one">
            <div key="B">B</div><div key="A">A</div>
          </div>
          <div key="two">
            <div key="D">D</div><div key="C">C</div>
          </div>
        </div>,
        container,
      );
      expect(container.textContent).toBe('BADC');
    });
  });
  describe('createOpenTagMarkup', () => {
    function quoteRegexp(str) {
      return (str + '').replace(/([.?*+\^$\[\]\\(){}|-])/g, '\\$1');
    }
    function toHaveAttribute(actual, expected) {
      var [attr, value] = expected;
      var re = '(?:^|\\s)' + attr + '=[\\\'"]';
      if (typeof value !== 'undefined') {
        re += quoteRegexp(value) + '[\\\'"]';
      }
      return new RegExp(re).test(actual);
    }
    function genMarkup(props) {