**Do you want to request a _feature_ or report a _bug_?**

Report a bug.

**What is the current behavior?**

When testing components, `Warning: ReactComponentTreeDevtool: Missing React element for debugID 1 when building stack` is shown when calling `TestUtils.renderIntoDocument`.

**If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem via https://jsfiddle.net or similar (template: https://jsfiddle.net/reactjs/69z2wepo/).**

https://github.com/angusfretwell/reproduce-debugid-warning (`npm install && npm test`).

**What is the expected behavior?**

According to #7187 this is an internal warning and shouldn't be displayed.

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**
- react@15.2.1
- react-addons-test-utils@15.2.1
- react-dom@15.2.1

I didn't receive this warning on 15.2.0.

* points to the correct divs.
       */
      return (
        <div>
          <div
            className="first"
            ref={count % 3 === 0 ? 'hopRef' : 'divOneRef'}
          />
          <div
            className="second"
            ref={count % 3 === 1 ? 'hopRef' : 'divTwoRef'}
          />
          <div
            className="third"
            ref={count % 3 === 2 ? 'hopRef' : 'divThreeRef'}
          />
        </div>
      );
    },
  });
  it('Allow refs to hop around children correctly', function() {
    var refHopsAround = ReactTestUtils.renderIntoDocument(<RefHopsAround />);
    var firstDiv =
      ReactTestUtils.findRenderedDOMComponentWithClass(refHopsAround, 'first');
    var secondDiv =
      ReactTestUtils.findRenderedDOMComponentWithClass(refHopsAround, 'second');
    var thirdDiv =
      ReactTestUtils.findRenderedDOMComponentWithClass(refHopsAround, 'third');
    expect(refHopsAround.refs.hopRef).toEqual(firstDiv);
    expect(refHopsAround.refs.divTwoRef).toEqual(secondDiv);