Tests: Remove shared subscriptions across parallel tests (#669)

In samples/snippets/noxfile.py, tests are run in parallel if pytest-parallel is installed.

This resulted in tests failing in CI that did not fail locally. Because of the use of shared subscription names across tests running in parallel, some tests were deleting a subscription, while others were attempting to receive messages.

This PR removes all subscription test fixtures that created and deleted subscriptions that were reused across tests in samples/snippets/subscriber_test.py, instead repeating the creation logic within each test, with a different subscription name per test, to allow tests to run in parallel without failures.

Also includes unrelated formatting changes due to linting changes.

Fixes #668🦕

samples/snippets/publisher_test.py

@@ -28,13 +28,18 @@
 import publisher
 
 
+# This uuid is shared across tests which run in parallel.
 UUID = uuid.uuid4().hex
 PROJECT_ID = os.environ["GOOGLE_CLOUD_PROJECT"]
 TOPIC_ID = "publisher-test-topic-" + UUID
 SUBSCRIPTION_ID = "publisher-test-subscription-" + UUID
 # Allow 60s for tests to finish.
 MAX_TIME = 60
 
+# These tests run in parallel if pytest-parallel is installed.
+# Avoid modifying resources that are shared across tests,
+# as this results in test flake.
+
 if typing.TYPE_CHECKING:
     from unittest.mock import AsyncMock, MagicMock
 

samples/snippets/schema_test.py

@@ -31,6 +31,7 @@
 
 import schema
 
+# This uuid is shared across tests which run in parallel.
 UUID = uuid.uuid4().hex
 try:
     PROJECT_ID = os.environ["GOOGLE_CLOUD_PROJECT"]
@@ -45,6 +46,10 @@
 AVSC_FILE = "resources/us-states.avsc"
 PROTO_FILE = "resources/us-states.proto"
 
+# These tests run in parallel if pytest-parallel is installed.
+# Avoid modifying resources that are shared across tests,
+# as this results in test flake.
+
 
 @pytest.fixture(scope="module")
 def schema_client() -> Generator[pubsub_v1.SchemaServiceClient, None, None]: