<!--
  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

);
    const tree = renderer.toTree();
    cleanNodeOrArray(tree);
    expect(prettyFormat(tree)).toEqual(
      prettyFormat({
        type: Foo,
        nodeType: 'component',
        props: {},
        instance: null,
        rendered: [
          {
            instance: null,
            nodeType: 'host',
            props: {},
            rendered: ['One'],
            type: 'div',
          },
          {
            instance: null,
            nodeType: 'host',
            props: {},
            rendered: ['Two'],
            type: 'div',
          },
        ],
      }),
    );
  });
  it('toTree() handles complicated tree of fragments', () => {
    class Foo extends React.Component {