Improve the imagetree test.

test/test_imagetree.py

@@ -20,7 +20,8 @@ class TestImageTree(unittest.TestCase):
     finished_database_for_testing(self)
     self.ctx.__exit__(True, None, None)
 
-  def _get_base_image(self, all_images):
+  @staticmethod
+  def _get_base_image(all_images):
     for image in all_images:
       if image.ancestors == '/':
         return image
@@ -90,29 +91,27 @@ class TestImageTree(unittest.TestCase):
     # still return the tag that contains them.
     self.assertEquals('staging', tree.tag_containing_image(result[0]))
 
-
   def test_longest_path_simple_repo_direct_lookup(self):
     repository = model.repository.get_repository(NAMESPACE, SIMPLE_REPO)
     all_images = list(model.image.get_repository_images(NAMESPACE, SIMPLE_REPO))
     all_tags = list(model.tag.list_repository_tags(NAMESPACE, SIMPLE_REPO))
 
     base_image = self._get_base_image(all_images)
-    tag_image = all_tags[0].image
 
     def checker(index, image):
       return True
 
-    filtered_images = model.image.get_repository_images_without_placements(repository,
-                                                                     with_ancestor=base_image)
+    filtered_images = model.image.get_repository_images_without_placements(
+      repository,
+      with_ancestor=base_image)
     self.assertEquals(set([f.id for f in filtered_images]), set([a.id for a in all_images]))
 
     tree = ImageTree(filtered_images, all_tags)
 
-    ancestors = tag_image.ancestors.split('/')[2:-1] # Skip the first image.
     result = tree.find_longest_path(base_image.id, checker)
     self.assertEquals(3, len(result))
     self.assertEquals('latest', tree.tag_containing_image(result[-1]))
 
+
 if __name__ == '__main__':
   unittest.main()
-