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  Note: if the issue is about documentation or the website, please file it at:
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**Do you want to request a *feature* or report a *bug*?**

bug.

**What is the current behavior?**

```js
  renderer.create(
    <Fragment>
      <Fragment>foo</Fragment>
    </Fragment>
  )
  .toTree()
```

> Invariant Violation: toTree() does not yet know how to handle nodes with tag=10

https://codesandbox.io/s/olky92m01y

**What is the expected behavior?**

returns a tree.

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**

16.2.0

invariant(
      validWrapperTypes.has(fiber.tag),
      'Unexpected object passed to ReactTestInstance constructor (tag: %s). ' +
        'This is probably a bug in React.',
      fiber.tag,
    );
    this._fiber = fiber;
  }
  get instance() {
    if (this._fiber.tag === HostComponent) {
      return getPublicInstance(this._fiber.stateNode);
    } else {
      return this._fiber.stateNode;
    }
  }
  get type() {
    return this._fiber.type;
  }
  get props(): Object {
    return this._currentFiber().memoizedProps;
  }
  get parent(): ?ReactTestInstance {
    const parent = this._fiber.return;
    return parent === null || parent.tag === HostRoot
      ? null
      : wrapFiber(parent);
  }
  get children(): Array<ReactTestInstance | string> {