**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.

ReactTestUtils.Simulate.click(clickIncrementer);
    expectClickLogsLengthToBe(testRefsComponent, 3);
    
    ReactTestUtils.Simulate.click(testRefsComponent.refs.resetDiv);
    expectClickLogsLengthToBe(testRefsComponent, 1);
  });
});
/**
 * Tests that when a ref hops around children, we can track that correctly.
 */
describe('ref swapping', function() {
  beforeEach(function() {
    jest.resetModuleRegistry();
    React = require('React');
    ReactTestUtils = require('ReactTestUtils');
    reactComponentExpect = require('reactComponentExpect');
  });
  var RefHopsAround = React.createClass({
    getInitialState: function() {
      return {count: 0};
    },
    moveRef: function() {
      this.setState({count: this.state.count + 1});
    },
    render: function() {
      var count = this.state.count;
      /**
       * What we have here, is three divs with refs (div1/2/3), but a single
       * moving cursor ref `hopRef` that "hops" around the three. We'll call the
       * `moveRef()` function several times and make sure that the hop ref