**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.

return (
      <div>
        {this.state.internalState}
      </div>
    );
  },
});
/**
 * Displays friends statuses.
 */
var FriendsStatusDisplay = React.createClass({
  /**
  * Gets the order directly from each rendered child's `index` field.
  * Refs are not maintained in the rendered order, and neither is
  * `this._renderedChildren` (surprisingly).
  */
  getOriginalKeys: function() {
    var originalKeys = [];
    
    
    var statusDisplays =
      ReactInstanceMap.get(this)
      ._renderedComponent
      ._renderedChildren;
    var name;
    for (name in statusDisplays) {
      var child = statusDisplays[name];
      var isPresent = !!child;
      if (isPresent) {
        originalKeys[child._mountIndex] = getOriginalKey(name);