[Findit] A huge refactoring and some bug fixing.

appengine/findit/model/test/versioned_model_test.py

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 from google.appengine.api import datastore_errors
 from google.appengine.ext import ndb
 
 from testing_utils import testing
 
 from model.versioned_model import VersionedModel
@@ skipping 41 matching lines @@
     self.assertIsNone(_Entity.GetVersion(0))
     self.assertIsNone(_Entity.GetVersion(3))
 
   def testGetLatestVersionNumber(self):
     root_key = ndb.Key('_EntityRoot', 1)
     _Entity._GetRootModel()(key=root_key, current=1).put()
     _Entity(key=ndb.Key('_Entity', 1, parent=root_key), value=2).put()
 
     self.assertEqual(1, _Entity.GetLatestVersionNumber())
 
+  def testGetLatestVersionNumberWhenNoRecordYet(self):
+    self.assertEqual(-1, _Entity.GetLatestVersionNumber())
+
   def testSaveNewVersion(self):
     entity = _Entity()
     entity.value = 1
     key = entity.Save()
 
     expected_key = ndb.Key('_EntityRoot', 1, '_Entity', 1)
     self.assertEqual(expected_key, key)
 
     entity = _Entity.GetVersion()
     self.assertEqual(1, entity.version)
@@ skipping 39 matching lines @@
         calls.append(1)
         raise datastore_errors.BadRequestError()
       return original_ndb_transaction(func, **options)
     self.mock(ndb, 'transaction', MockNdbTransaction)
 
     entity = _Entity()
     key = entity.Save()
     expected_key = ndb.Key('_EntityRoot', 1, '_Entity', 1)
     self.assertEqual(expected_key, key)
     self.assertEqual([1], calls)