Something like this?

        # right params but with duplicates
        request = mock.MagicMock(wraps=Request('http://a.b/path/'))
        request.duplicate_params = ['scope']
        self.assertRaises(InvalidRequestError, auth.validate_token_request,
                          request)
        # wrong grant type
        request = mock.MagicMock(wraps=Request('http://a.b/path'))
        request.grant_type = 'foo'
        self.assertRaises(UnsupportedGrantTypeError,
                          auth.validate_token_request, request)