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

**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

children: null,
          props: {},
        },
      ],
      props: {},
    });
  });
  it('toTree() renders simple components returning host components', () => {
    const Qoo = () => <span className="Qoo">Hello World!</span>;
    const renderer = ReactTestRenderer.create(<Qoo />);
    const tree = renderer.toTree();
    cleanNodeOrArray(tree);
    expect(prettyFormat(tree)).toEqual(
      prettyFormat({
        nodeType: 'component',
        type: Qoo,
        props: {},
        instance: null,
        rendered: {
          nodeType: 'host',
          type: 'span',
          props: {className: 'Qoo'},
          instance: null,
          rendered: ['Hello World!'],
        },
      }),
    );
  });
  it('toTree() handles null rendering components', () => {
    class Foo extends React.Component {