class MyModel(db.Model):
    name = db.StringProperty()
    code = db.IntegerProperty()

class MyHandler(webapp2.RequestHandler):

    def MyMethod(self, name):
        if self.request.method == 'POST':
            model = MyModel.gql("WHERE name=:1", name).get()
            model.code = SOME_CODE
            model.put()

from google.appengine.ext import testbed
import unittest
import webtest
import MyModel
from main import api_routes '''my WSGIapplication routes '''

class MyTestClass(unittest.TestCase):

    def setUp(self):
        app = webapp2.WSGIApplication(routes=api_routes)
        self.testapp = webtest.TestApp(app)
        self.testbed = testbed.Testbed()
        self.testbed.activate()
        self.testbed.init_datastore_v3_stub()
        self.testmodel = MyModel(name='testname')
        self.testmodel.put()

    def tearDown(self):
        self.testbed.deactivate()

    def testOne(self):
        url = SOME_URL # which call MyHandler MyMethod
        params = {'name':'testname'}
        response = self.testapp.post(url,params)
        SOMEASSERTS

def testOne(self):
        url = SOME_URL # which call MyHandler MyMethod
        params = {'name':'testname'}
        response = self.testapp.post(url,params)
        model = MyModel.gql("WHERE name=:1",'testname').get()
        self.assertTrue(model.code == SOME_CODE)