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**Do you want to request a *feature* or report a *bug*?** Bug, I guess

**What is the current behavior?** 


```
  console.error node_modules/fbjs/lib/warning.js:33
    Warning: Detected multiple renderers concurrently rendering the same context provider. This is currently unsupported.
```

Steps to reproduce the behavior:
1. `git clone https://github.com/stereobooster/react-context-issue`
2. `cd react-context-issue`
3. `yarn`
4. `yarn test`

**What is the expected behavior?** no warning

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?** React 16.4. Browser not affected, because error is in node.js

Open this because of https://github.com/facebook/react/pull/13127#issuecomment-402527012

Issue happens because of Enzyme (https://github.com/airbnb/enzyme/issues/1693), code is unreleased, so I copy-pasted it from master. 

I'm looking for advice or some clue on how to fix this, so I would be able to create PR in Enzyme repo (or in React repo if this is the case). Thank you.


render() {
        return <div ref="baz" />;
      }
    }
    ReactTestRenderer.create(<Baz />);
    expect(() => ReactTestRenderer.create(<Foo />)).toWarnDev(
      'Warning: Stateless function components cannot be given refs. Attempts ' +
        'to access this ref will fail.\n\nCheck the render method of `Foo`.\n' +
        '    in Bar (at **)\n' +
        '    in Foo (at **)',
    );
  });
  it('allows an optional createNodeMock function', () => {
    const mockDivInstance = {appendChild: () => {}};
    const mockInputInstance = {focus: () => {}};
    const mockListItemInstance = {click: () => {}};
    const mockAnchorInstance = {hover: () => {}};
    const log = [];
    class Foo extends React.Component {
      componentDidMount() {
        log.push(this.refs.bar);
      }
      render() {
        return <a ref="bar">Hello, world</a>;
      }
    }
    function createNodeMock(element) {