Just about every time I set up a new `Context.Provider`, I end up accidentally specifying a `values` prop rather than `value`.  While it's a minor error, generally I build the container in which the provider resides and commit it to the code base before I ever use it.  It's only later when I go to use it that I realize I did it again.  Since the `Context.Provider` seems pretty much useless without a `value` prop specified, I'd love it if there was a prop error if it is missing... especially if another prop is defined on the `Context.Provider` instead.
<ParentContextProvider>
          <ComponentA />
        </ParentContextProvider>,
      ),
    ).toErrorDev(
      'Warning: ComponentA declares both contextTypes and contextType static properties. ' +
        'The legacy contextTypes property will be ignored.',
    );
    
    ReactTestUtils.renderIntoDocument(
      <ParentContextProvider>
        <ComponentA />
      </ParentContextProvider>,
    );
    expect(() =>
      ReactTestUtils.renderIntoDocument(
        <ParentContextProvider>
          <ComponentB />
        </ParentContextProvider>,
      ),
    ).toErrorDev(
      'Warning: ComponentB declares both contextTypes and contextType static properties. ' +
        'The legacy contextTypes property will be ignored.',
    );
  });
  it('should warn if an invalid contextType is defined', () => {
    const Context = React.createContext();
    
    
    class ComponentA extends React.Component {