<!--
  Note: if the issue is about documentation or the website, please file it at:
  https://github.com/reactjs/reactjs.org/issues/new
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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

for (const key in filter) {
    if (props[key] !== filter[key]) {
      return false;
    }
  }
  return true;
}
const ReactTestRendererFiber = {
  create(element: React$Element<any>, options: TestRendererOptions) {
    let createNodeMock = defaultTestOptions.createNodeMock;
    if (options && typeof options.createNodeMock === 'function') {
      createNodeMock = options.createNodeMock;
    }
    let container = {
      children: [],
      createNodeMock,
      tag: 'CONTAINER',
    };
    let root: FiberRoot | null = TestRenderer.createContainer(
      container,
      false,
      false,
    );
    invariant(root != null, 'something went wrong');
    TestRenderer.updateContainer(element, root, null, null);
    const entry = {
      root: undefined, 
      
      toJSON() {