diff --git a/HACKING.rst b/HACKING.rst
index f961884..bb55ac5 100644
--- a/HACKING.rst
+++ b/HACKING.rst
@@ -363,13 +363,24 @@
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 When adding tests for new features that were not in previous releases of the
-projects the new test has to be properly skipped with a feature flag. Whether
-this is just as simple as using the @utils.requires_ext() decorator to
-check if the required extension (or discoverable optional API) is enabled or
+projects the new test has to be properly skipped with a feature flag. This can
+be just as simple as using the ``@utils.requires_ext()`` or
+``testtools.skipUnless`` decorators to check if the required extension (or
+discoverable optional API) or feature is enabled or can be as difficult as
 adding a new config option to the appropriate section. If there isn't a method
 of selecting the new **feature** from the config file then there won't be a
-mechanism to disable the test with older stable releases and the new test won't
-be able to merge.
+mechanism to disable the test with older stable releases and the new test
+won't be able to merge.
+
+Introduction of a new feature flag requires specifying a default value for
+the corresponding config option that is appropriate in the latest OpenStack
+release. Because Tempest is branchless, the feature flag's default value will
+need to be overridden to a value that is appropriate in earlier releases
+in which the feature isn't available. In DevStack, this can be accomplished
+by modifying Tempest's `lib installation script`_ for previous branches
+(because DevStack is branched).
+
+.. _lib installation script: http://git.openstack.org/cgit/openstack-dev/devstack/tree/lib/tempest
 
 2. Bug fix on core project needing Tempest changes
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/tempest/api/volume/test_volumes_extend.py b/tempest/api/volume/test_volumes_extend.py
index 54052ae..362f4cc 100644
--- a/tempest/api/volume/test_volumes_extend.py
+++ b/tempest/api/volume/test_volumes_extend.py
@@ -32,7 +32,7 @@
     @decorators.idempotent_id('9a36df71-a257-43a5-9555-dc7c88e66e0e')
     def test_volume_extend(self):
         # Extend Volume Test.
-        volume = self.create_volume()
+        volume = self.create_volume(image_ref=self.image_ref)
         extend_size = volume['size'] + 1
         self.volumes_client.extend_volume(volume['id'],
                                           new_size=extend_size)
diff --git a/tempest/api/volume/test_volumes_snapshots.py b/tempest/api/volume/test_volumes_snapshots.py
index dcd3518..52114bc 100644
--- a/tempest/api/volume/test_volumes_snapshots.py
+++ b/tempest/api/volume/test_volumes_snapshots.py
@@ -41,16 +41,19 @@
     def test_snapshot_create_delete_with_volume_in_use(self):
         # Create a test instance
         server = self.create_server()
-        self.attach_volume(server['id'], self.volume_origin['id'])
+        # NOTE(zhufl) Here we create volume from self.image_ref for adding
+        # coverage for "creating snapshot from non-blank volume".
+        volume = self.create_volume(image_ref=self.image_ref)
+        self.attach_volume(server['id'], volume['id'])
 
         # Snapshot a volume which attached to an instance with force=False
         self.assertRaises(lib_exc.BadRequest, self.create_snapshot,
-                          self.volume_origin['id'], force=False)
+                          volume['id'], force=False)
 
         # Snapshot a volume attached to an instance
-        snapshot1 = self.create_snapshot(self.volume_origin['id'], force=True)
-        snapshot2 = self.create_snapshot(self.volume_origin['id'], force=True)
-        snapshot3 = self.create_snapshot(self.volume_origin['id'], force=True)
+        snapshot1 = self.create_snapshot(volume['id'], force=True)
+        snapshot2 = self.create_snapshot(volume['id'], force=True)
+        snapshot3 = self.create_snapshot(volume['id'], force=True)
 
         # Delete the snapshots. Some snapshot implementations can take
         # different paths according to order they are deleted.