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

**What is the current behavior?**
The shallow renderer defaults a class component's state to empty object if it's not set. "Real" renderers don't seem to do this, so a component can render successfully in the shallow renderer, but fail at runtime in the browser with a null reference error.

**If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem.**
Here is ReactDOM's behavior (crashes reading an uninitialized state value): https://codesandbox.io/s/4jv82zmp0
Here is the shallow renderer behavior (component able to render): https://codesandbox.io/s/pp733nrxzq

**What is the expected behavior?**
They initialize state in the same way.

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**
React 16. This wasn't an issue in React 15.
return <div>{this.context.name}</div>;
      }
    }
    const shallowRenderer = createRenderer();
    expect(() => shallowRenderer.render(<SimpleComponent />)).toWarnDev(
      'Warning: Failed context type: The context `name` is marked as ' +
        'required in `SimpleComponent`, but its value is `undefined`.\n' +
        '    in SimpleComponent (at **)',
    );
  });
  it('should warn about propTypes (but only once)', () => {
    class SimpleComponent extends React.Component {
      render() {
        return React.createElement('div', null, this.props.name);
      }
    }
    SimpleComponent.propTypes = {
      name: PropTypes.string.isRequired,
    };
    const shallowRenderer = createRenderer();
    expect(() =>
      shallowRenderer.render(React.createElement(SimpleComponent, {name: 123})),
    ).toWarnDev(
      'Warning: Failed prop type: Invalid prop `name` of type `number` ' +
        'supplied to `SimpleComponent`, expected `string`.\n' +
        '    in SimpleComponent',
    );
  });
  it('should enable rendering of cloned element', () => {
    class SimpleComponent extends React.Component {