<!--
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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.


nodeType: 'host',
          props: {},
          instance: null,
          rendered: ['Four'],
        },
      ]),
    );
  });
  it('root instance and createNodeMock ref return the same value', () => {
    const createNodeMock = ref => ({node: ref});
    let refInst = null;
    const renderer = ReactTestRenderer.create(
      <div ref={ref => (refInst = ref)} />,
      {createNodeMock},
    );
    const root = renderer.getInstance();
    expect(root).toEqual(refInst);
  });
  it('toTree() renders complicated trees of composites and hosts', () => {
    
    const Qoo = () => <span className="Qoo">Hello World!</span>;
    
    const Foo = ({className, children}) => (
      <div className={'Foo ' + className}>
        <span className="Foo2">Literal</span>
        {children}
      </div>
    );
    
    class Bar extends React.Component {