Right now we validate some of our proptype definitions, but we don't surface the issue until that component class is consumed. We should instead validate these, in `__DEV__` only as warnings when the class in created. This means that a call to `React.PropTypes.onOf('foo')` results in an immediate warning logged.

This is a relatively contained bit of code so would be a good candidate for somebody looking to start contributing to React.

});
  describe('Shape Types', function() {
    it('should warn for non objects', function() {
      typeCheckFail(
        PropTypes.shape({}),
        'some string',
        'Invalid prop `testProp` of type `string` supplied to ' +
        '`testComponent`, expected `object`.'
      );
      typeCheckFail(
        PropTypes.shape({}),
        ['array'],
        'Invalid prop `testProp` of type `array` supplied to ' +
        '`testComponent`, expected `object`.'
      );
    });
    it('should not warn for empty values', function() {
      typeCheckPass(PropTypes.shape({}), undefined);
      typeCheckPass(PropTypes.shape({}), null);
      typeCheckPass(PropTypes.shape({}), {});
    });
    it('should not warn for an empty object', function() {
      typeCheckPass(PropTypes.shape({}).isRequired, {});
    });
    it('should not warn for non specified types', function() {
      typeCheckPass(PropTypes.shape({}), {key: 1});
    });
    it('should not warn for valid types', function() {
      typeCheckPass(PropTypes.shape({key: PropTypes.number}), {key: 1});
    });