Add a squashing test for images with empty layers

test/registry/registry_tests.py

@@ -1575,6 +1575,32 @@ def test_push_pull_manifest_list_duplicate_manifest(v22_protocol, basic_images,
                          credentials=credentials, options=options)
 
 
+def test_squashed_images_empty_layer(pusher, images_with_empty_layer, liveserver_session,
+                                     liveserver, registry_server_executor, app_reloader):
+  """ Test: Pulling of squashed images for a manifest with empty layers. """
+  credentials = ('devtable', 'password')
+
+  # Push an image to download.
+  pusher.push(liveserver_session, 'devtable', 'newrepo', 'latest', images_with_empty_layer,
+              credentials=credentials)
+
+  # Pull the squashed version.
+  response = liveserver_session.get('/c1/squash/devtable/newrepo/latest', auth=credentials)
+  assert response.status_code == 200
+
+  tar = tarfile.open(fileobj=StringIO(response.content))
+
+  # Verify the squashed image.
+  expected_image_id = 'cdc6d6c0d07d2cbacfc579e49ce0c256c5084b9b2b16c1b1b0c45f26a12a4ba5'
+  expected_names = ['repositories',
+                    expected_image_id,
+                    '%s/json' % expected_image_id,
+                    '%s/VERSION' % expected_image_id,
+                    '%s/layer.tar' % expected_image_id]
+
+  assert tar.getnames() == expected_names
+
+
 def test_squashed_image_unsupported(v22_protocol, basic_images, liveserver_session, liveserver,
                                     app_reloader, data_model):
   """ Test: Attempting to pull a squashed image for a manifest list without an amd64+linux entry.