How to use the webtest.utils function in WebTest

    def _gen_request(self, method, url, params=utils.NoDefault,
                     headers=None, extra_environ=None, status=None,
                     upload_files=None, expect_errors=False,
                     content_type=None, auth=None, auth_type=None, **kwargs):
        """Do a generic request.
        """
        return super(TestApp, self)._gen_request(method=method,
                                                url=url,
                                                params=params,
                                                headers=self._build_headers(
                                                    headers, auth, auth_type),
                                                extra_environ=extra_environ,
                                                status=status,
                                                upload_files=upload_files,
                                                expect_errors=expect_errors,
                                                content_type=content_type,
                                                **kwargs)

pass
        res.errors = errors.getvalue()

        for name, value in req.environ['paste.testing_variables'].items():
            if hasattr(res, name):
                raise ValueError(
                    "paste.testing_variables contains the variable %r, but "
                    "the response object already has an attribute by that "
                    "name" % name)
            setattr(res, name, value)
        if not expect_errors:
            self._check_status(status, res)
            self._check_errors(res)

        # merge cookies back in
        self.cookiejar.extract_cookies(utils._ResponseCookieAdapter(res),
                                       utils._RequestCookieAdapter(req))

        return res

def head(self, url, headers=None, extra_environ=None,
             status=None, expect_errors=False, xhr=False):
        """
        Do a HEAD request. Similar to :meth:`~webtest.TestApp.get`.

        :returns: :class:`webtest.TestResponse` instance.

        """
        if xhr:
            headers = self._add_xhr_header(headers)
        return self._gen_request('HEAD', url, headers=headers,
                                 extra_environ=extra_environ, status=status,
                                 upload_files=None,
                                 expect_errors=expect_errors)

    post_json = utils.json_method('POST')
    put_json = utils.json_method('PUT')
    patch_json = utils.json_method('PATCH')
    delete_json = utils.json_method('DELETE')

    def encode_multipart(self, params, files):
        """
        Encodes a set of parameters (typically a name/value list) and
        a set of files (a list of (name, filename, file_body, mimetype)) into a
        typical POST body, returning the (content_type, body).

        """
        boundary = to_bytes(str(random.random()))[2:]
        boundary = b'----------a_BoUnDaRy' + boundary + b'$'
        lines = []

        def _append_file(file_info):

def test_stringify_text(self):
        self.assertEqual(utils.stringify("foo"), "foo")

    def delete(self, url, params=utils.NoDefault, headers=None,
               extra_environ=None, status=None, expect_errors=False,
               content_type=None, xhr=False, auth=None, auth_type=None, **kwargs):
        return super(TestApp, self).delete(
                        url=url, params=params,
                        headers=self._build_headers(headers, auth, auth_type),
                        extra_environ=extra_environ,
                        status=status,
                        expect_errors=expect_errors,
                        content_type=content_type, xhr=xhr, **kwargs)