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.
switch (element.type) {
        case 'div':
          return mockDivInstance;
        case 'input':
          return mockInputInstance;
        case 'li':
          return mockListItemInstance;
        case 'a':
          return mockAnchorInstance;
        default:
          return {};
      }
    }
    ReactTestRenderer.create(<div ref={r => log.push(r)} />, {createNodeMock});
    ReactTestRenderer.create(<input ref={r => log.push(r)} />, {
      createNodeMock,
    });
    ReactTestRenderer.create(
      <div>
        <span>
          <ul>
            <li ref={r => log.push(r)} />
          </ul>
          <ul>
            <li ref={r => log.push(r)} />
            <li ref={r => log.push(r)} />
          </ul>
        </span>
      </div>,