diff --git a/.github/.OwlBot.lock.yaml b/.github/.OwlBot.lock.yaml
index fb0f61e8..d57f7420 100644
--- a/.github/.OwlBot.lock.yaml
+++ b/.github/.OwlBot.lock.yaml
@@ -1,4 +1,3 @@
 docker:
   image: gcr.io/repo-automation-bots/owlbot-python:latest
-  digest: sha256:5ff7446edeaede81c3ed58b23a4e76a5403fba1350ce28478045657303b6479d
-
+  digest: sha256:6186535cbdbf6b9fe61f00294929221d060634dae4a0795c1cefdbc995b2d605
diff --git a/CONTRIBUTING.rst b/CONTRIBUTING.rst
index a09a0802..26ea1fac 100644
--- a/CONTRIBUTING.rst
+++ b/CONTRIBUTING.rst
@@ -177,6 +177,30 @@ Build the docs via:
 
    $ nox -s docs
 
+*************************
+Samples and code snippets
+*************************
+
+Code samples and snippets live in the `samples/` catalogue. Feel free to
+provide more examples, but make sure to write tests for those examples.
+Each folder containing example code requires its own `noxfile.py` script
+which automates testing. If you decide to create a new folder, you can
+base it on the `samples/snippets` folder (providing `noxfile.py` and
+the requirements files).
+
+The tests will run against a real Google Cloud Project, so you should
+configure them just like the System Tests.
+
+- To run sample tests, you can execute::
+
+   # Run all tests in a folder
+   $ cd samples/snippets
+   $ nox -s py-3.8
+
+   # Run a single sample test
+   $ cd samples/snippets
+   $ nox -s py-3.8 -- -k <name of test>
+
 ********************************************
 Note About ``README`` as it pertains to PyPI
 ********************************************
diff --git a/samples/snippets/manage_transfer_configs.py b/samples/snippets/manage_transfer_configs.py
index 6b4abd78..5f775f10 100644
--- a/samples/snippets/manage_transfer_configs.py
+++ b/samples/snippets/manage_transfer_configs.py
@@ -135,9 +135,7 @@ def schedule_backfill(override_values={}):
     )
 
     response = transfer_client.schedule_transfer_runs(
-        parent=transfer_config_name,
-        start_time=start_time,
-        end_time=end_time,
+        parent=transfer_config_name, start_time=start_time, end_time=end_time,
     )
 
     print("Started transfer runs:")
diff --git a/samples/snippets/noxfile.py b/samples/snippets/noxfile.py
index b3c8658a..9fc7f178 100644
--- a/samples/snippets/noxfile.py
+++ b/samples/snippets/noxfile.py
@@ -28,8 +28,9 @@
 # WARNING - WARNING - WARNING - WARNING - WARNING
 # WARNING - WARNING - WARNING - WARNING - WARNING
 
-# Copy `noxfile_config.py` to your directory and modify it instead.
+BLACK_VERSION = "black==19.10b0"
 
+# Copy `noxfile_config.py` to your directory and modify it instead.
 
 # `TEST_CONFIG` dict is a configuration hook that allows users to
 # modify the test configurations. The values here should be in sync
@@ -159,7 +160,7 @@ def lint(session: nox.sessions.Session) -> None:
 
 @nox.session
 def blacken(session: nox.sessions.Session) -> None:
-    session.install("black")
+    session.install(BLACK_VERSION)
     python_files = [path for path in os.listdir(".") if path.endswith(".py")]
 
     session.run("black", *python_files)
@@ -226,7 +227,7 @@ def py(session: nox.sessions.Session) -> None:
 
 
 def _get_repo_root() -> Optional[str]:
-    """Returns the root folder of the project."""
+    """ Returns the root folder of the project. """
     # Get root of this repository. Assume we don't have directories nested deeper than 10 items.
     p = Path(os.getcwd())
     for i in range(10):
diff --git a/samples/snippets/run_notification_test.py b/samples/snippets/run_notification_test.py
index 02f24266..4c41e689 100644
--- a/samples/snippets/run_notification_test.py
+++ b/samples/snippets/run_notification_test.py
@@ -17,8 +17,7 @@
 
 def test_run_notification(capsys, transfer_config_name, pubsub_topic):
     run_notification.run_notification(
-        transfer_config_name=transfer_config_name,
-        pubsub_topic=pubsub_topic,
+        transfer_config_name=transfer_config_name, pubsub_topic=pubsub_topic,
     )
     out, _ = capsys.readouterr()
     assert "Updated config:" in out