diff --git a/.coveragerc b/.coveragerc
index 38dd96f7..63daceaf 100644
--- a/.coveragerc
+++ b/.coveragerc
@@ -2,7 +2,6 @@
 branch = True
 
 [report]
-fail_under = 100
 show_missing = True
 omit =
     google/cloud/bigquery_datatransfer/__init__.py
diff --git a/.github/.OwlBot.lock.yaml b/.github/.OwlBot.lock.yaml
index 0954585f..e2b39f94 100644
--- a/.github/.OwlBot.lock.yaml
+++ b/.github/.OwlBot.lock.yaml
@@ -1,3 +1,3 @@
 docker:
   image: gcr.io/repo-automation-bots/owlbot-python:latest
-  digest: sha256:df50e8d462f86d6bcb42f27ecad55bb12c404f1c65de9c6fe4c4d25120080bd6
+  digest: sha256:99d90d097e4a4710cc8658ee0b5b963f4426d0e424819787c3ac1405c9a26719
diff --git a/CHANGELOG.md b/CHANGELOG.md
index ce1b11ae..6af254d8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,18 @@
 
 [1]: https://pypi.org/project/google-cloud-bigquery-datatransfer/#history
 
+## [3.3.0](https://www.github.com/googleapis/python-bigquery-datatransfer/compare/v3.2.0...v3.3.0) (2021-07-12)
+
+
+### Features
+
+* add always_use_jwt_access ([#171](https://www.github.com/googleapis/python-bigquery-datatransfer/issues/171)) ([cd4494f](https://www.github.com/googleapis/python-bigquery-datatransfer/commit/cd4494f0dc7304469e7d4a0ed6e13d716b3cacbf))
+
+
+### Documentation
+
+* add sample to include run notification ([#173](https://www.github.com/googleapis/python-bigquery-datatransfer/issues/173)) ([ea018c9](https://www.github.com/googleapis/python-bigquery-datatransfer/commit/ea018c9f4a1f9c360dbe9f08650250ea8c505f29))
+
 ## [3.2.0](https://www.github.com/googleapis/python-bigquery-datatransfer/compare/v3.1.1...v3.2.0) (2021-06-22)
 
 
diff --git a/CONTRIBUTING.rst b/CONTRIBUTING.rst
index 5165217c..a09a0802 100644
--- a/CONTRIBUTING.rst
+++ b/CONTRIBUTING.rst
@@ -68,14 +68,12 @@ Using ``nox``
 We use `nox <https://nox.readthedocs.io/en/latest/>`__ to instrument our tests.
 
 - To test your changes, run unit tests with ``nox``::
+    $ nox -s unit
 
-    $ nox -s unit-3.8
-    $ ...
+- To run a single unit test::
 
-- Args to pytest can be passed through the nox command separated by a `--`. For
-  example, to run a single test::
+    $ nox -s unit-3.9 -- -k <name of test>
 
-    $ nox -s unit-3.8 -- -k <name of test>
 
   .. note::
 
@@ -142,7 +140,7 @@ Running System Tests
 - To run system tests, you can execute::
 
    # Run all system tests
-   $ nox -s system-3.8
+   $ nox -s system
 
    # Run a single system test
    $ nox -s system-3.8 -- -k <name of test>
@@ -215,8 +213,8 @@ Supported versions can be found in our ``noxfile.py`` `config`_.
 .. _config: https://github.com/googleapis/python-bigquery-datatransfer/blob/master/noxfile.py
 
 
-We also explicitly decided to support Python 3 beginning with version
-3.6. Reasons for this include:
+We also explicitly decided to support Python 3 beginning with version 3.6.
+Reasons for this include:
 
 -  Encouraging use of newest versions of Python 3
 -  Taking the lead of `prominent`_ open-source `projects`_
diff --git a/google/cloud/bigquery_datatransfer_v1/services/data_transfer_service/async_client.py b/google/cloud/bigquery_datatransfer_v1/services/data_transfer_service/async_client.py
index d0454623..7f502338 100644
--- a/google/cloud/bigquery_datatransfer_v1/services/data_transfer_service/async_client.py
+++ b/google/cloud/bigquery_datatransfer_v1/services/data_transfer_service/async_client.py
@@ -18,6 +18,7 @@
 import re
 from typing import Dict, Sequence, Tuple, Type, Union
 import pkg_resources
+import warnings
 
 import google.api_core.client_options as ClientOptions  # type: ignore
 from google.api_core import exceptions as core_exceptions  # type: ignore
@@ -861,6 +862,11 @@ async def schedule_transfer_runs(
                 for a time range.
 
         """
+        warnings.warn(
+            "DataTransferServiceAsyncClient.schedule_transfer_runs is deprecated",
+            DeprecationWarning,
+        )
+
         # Create or coerce a protobuf request object.
         # Sanity check: If we got a request object, we should *not* have
         # gotten any keyword arguments that map to the request.
diff --git a/google/cloud/bigquery_datatransfer_v1/services/data_transfer_service/client.py b/google/cloud/bigquery_datatransfer_v1/services/data_transfer_service/client.py
index b0dab00f..099e611b 100644
--- a/google/cloud/bigquery_datatransfer_v1/services/data_transfer_service/client.py
+++ b/google/cloud/bigquery_datatransfer_v1/services/data_transfer_service/client.py
@@ -19,6 +19,7 @@
 import re
 from typing import Callable, Dict, Optional, Sequence, Tuple, Type, Union
 import pkg_resources
+import warnings
 
 from google.api_core import client_options as client_options_lib  # type: ignore
 from google.api_core import exceptions as core_exceptions  # type: ignore
@@ -1020,6 +1021,11 @@ def schedule_transfer_runs(
                 for a time range.
 
         """
+        warnings.warn(
+            "DataTransferServiceClient.schedule_transfer_runs is deprecated",
+            DeprecationWarning,
+        )
+
         # Create or coerce a protobuf request object.
         # Sanity check: If we got a request object, we should *not* have
         # gotten any keyword arguments that map to the request.
diff --git a/google/cloud/bigquery_datatransfer_v1/services/data_transfer_service/transports/base.py b/google/cloud/bigquery_datatransfer_v1/services/data_transfer_service/transports/base.py
index 830861c5..d4a0ff10 100644
--- a/google/cloud/bigquery_datatransfer_v1/services/data_transfer_service/transports/base.py
+++ b/google/cloud/bigquery_datatransfer_v1/services/data_transfer_service/transports/base.py
@@ -24,6 +24,7 @@
 from google.api_core import gapic_v1  # type: ignore
 from google.api_core import retry as retries  # type: ignore
 from google.auth import credentials as ga_credentials  # type: ignore
+from google.oauth2 import service_account  # type: ignore
 
 from google.cloud.bigquery_datatransfer_v1.types import datatransfer
 from google.cloud.bigquery_datatransfer_v1.types import transfer
@@ -47,8 +48,6 @@
     except pkg_resources.DistributionNotFound:  # pragma: NO COVER
         _GOOGLE_AUTH_VERSION = None
 
-_API_CORE_VERSION = google.api_core.__version__
-
 
 class DataTransferServiceTransport(abc.ABC):
     """Abstract transport class for DataTransferService."""
@@ -66,6 +65,7 @@ def __init__(
         scopes: Optional[Sequence[str]] = None,
         quota_project_id: Optional[str] = None,
         client_info: gapic_v1.client_info.ClientInfo = DEFAULT_CLIENT_INFO,
+        always_use_jwt_access: Optional[bool] = False,
         **kwargs,
     ) -> None:
         """Instantiate the transport.
@@ -89,6 +89,8 @@ def __init__(
                 API requests. If ``None``, then default info will be used.
                 Generally, you only need to set this if you're developing
                 your own client library.
+            always_use_jwt_access (Optional[bool]): Whether self signed JWT should
+                be used for service account credentials.
         """
         # Save the hostname. Default to port 443 (HTTPS) if none is specified.
         if ":" not in host:
@@ -98,7 +100,7 @@ def __init__(
         scopes_kwargs = self._get_scopes_kwargs(self._host, scopes)
 
         # Save the scopes.
-        self._scopes = scopes or self.AUTH_SCOPES
+        self._scopes = scopes
 
         # If no credentials are provided, then determine the appropriate
         # defaults.
@@ -117,13 +119,20 @@ def __init__(
                 **scopes_kwargs, quota_project_id=quota_project_id
             )
 
+        # If the credentials is service account credentials, then always try to use self signed JWT.
+        if (
+            always_use_jwt_access
+            and isinstance(credentials, service_account.Credentials)
+            and hasattr(service_account.Credentials, "with_always_use_jwt_access")
+        ):
+            credentials = credentials.with_always_use_jwt_access(True)
+
         # Save the credentials.
         self._credentials = credentials
 
-    # TODO(busunkim): These two class methods are in the base transport
+    # TODO(busunkim): This method is in the base transport
     # to avoid duplicating code across the transport classes. These functions
-    # should be deleted once the minimum required versions of google-api-core
-    # and google-auth are increased.
+    # should be deleted once the minimum required versions of google-auth is increased.
 
     # TODO: Remove this function once google-auth >= 1.25.0 is required
     @classmethod
@@ -144,27 +153,6 @@ def _get_scopes_kwargs(
 
         return scopes_kwargs
 
-    # TODO: Remove this function once google-api-core >= 1.26.0 is required
-    @classmethod
-    def _get_self_signed_jwt_kwargs(
-        cls, host: str, scopes: Optional[Sequence[str]]
-    ) -> Dict[str, Union[Optional[Sequence[str]], str]]:
-        """Returns kwargs to pass to grpc_helpers.create_channel depending on the google-api-core version"""
-
-        self_signed_jwt_kwargs: Dict[str, Union[Optional[Sequence[str]], str]] = {}
-
-        if _API_CORE_VERSION and (
-            packaging.version.parse(_API_CORE_VERSION)
-            >= packaging.version.parse("1.26.0")
-        ):
-            self_signed_jwt_kwargs["default_scopes"] = cls.AUTH_SCOPES
-            self_signed_jwt_kwargs["scopes"] = scopes
-            self_signed_jwt_kwargs["default_host"] = cls.DEFAULT_HOST
-        else:
-            self_signed_jwt_kwargs["scopes"] = scopes or cls.AUTH_SCOPES
-
-        return self_signed_jwt_kwargs
-
     def _prep_wrapped_messages(self, client_info):
         # Precompute the wrapped methods.
         self._wrapped_methods = {
diff --git a/google/cloud/bigquery_datatransfer_v1/services/data_transfer_service/transports/grpc.py b/google/cloud/bigquery_datatransfer_v1/services/data_transfer_service/transports/grpc.py
index 9181ae48..6f431d2a 100644
--- a/google/cloud/bigquery_datatransfer_v1/services/data_transfer_service/transports/grpc.py
+++ b/google/cloud/bigquery_datatransfer_v1/services/data_transfer_service/transports/grpc.py
@@ -62,6 +62,7 @@ def __init__(
         client_cert_source_for_mtls: Callable[[], Tuple[bytes, bytes]] = None,
         quota_project_id: Optional[str] = None,
         client_info: gapic_v1.client_info.ClientInfo = DEFAULT_CLIENT_INFO,
+        always_use_jwt_access: Optional[bool] = False,
     ) -> None:
         """Instantiate the transport.
 
@@ -102,6 +103,8 @@ def __init__(
                 API requests. If ``None``, then default info will be used.
                 Generally, you only need to set this if you're developing
                 your own client library.
+            always_use_jwt_access (Optional[bool]): Whether self signed JWT should
+                be used for service account credentials.
 
         Raises:
           google.auth.exceptions.MutualTLSChannelError: If mutual TLS transport
@@ -154,6 +157,7 @@ def __init__(
             scopes=scopes,
             quota_project_id=quota_project_id,
             client_info=client_info,
+            always_use_jwt_access=always_use_jwt_access,
         )
 
         if not self._grpc_channel:
@@ -209,14 +213,14 @@ def create_channel(
               and ``credentials_file`` are passed.
         """
 
-        self_signed_jwt_kwargs = cls._get_self_signed_jwt_kwargs(host, scopes)
-
         return grpc_helpers.create_channel(
             host,
             credentials=credentials,
             credentials_file=credentials_file,
             quota_project_id=quota_project_id,
-            **self_signed_jwt_kwargs,
+            default_scopes=cls.AUTH_SCOPES,
+            scopes=scopes,
+            default_host=cls.DEFAULT_HOST,
             **kwargs,
         )
 
diff --git a/google/cloud/bigquery_datatransfer_v1/services/data_transfer_service/transports/grpc_asyncio.py b/google/cloud/bigquery_datatransfer_v1/services/data_transfer_service/transports/grpc_asyncio.py
index 2cd986db..a5f7d8f4 100644
--- a/google/cloud/bigquery_datatransfer_v1/services/data_transfer_service/transports/grpc_asyncio.py
+++ b/google/cloud/bigquery_datatransfer_v1/services/data_transfer_service/transports/grpc_asyncio.py
@@ -83,14 +83,14 @@ def create_channel(
             aio.Channel: A gRPC AsyncIO channel object.
         """
 
-        self_signed_jwt_kwargs = cls._get_self_signed_jwt_kwargs(host, scopes)
-
         return grpc_helpers_async.create_channel(
             host,
             credentials=credentials,
             credentials_file=credentials_file,
             quota_project_id=quota_project_id,
-            **self_signed_jwt_kwargs,
+            default_scopes=cls.AUTH_SCOPES,
+            scopes=scopes,
+            default_host=cls.DEFAULT_HOST,
             **kwargs,
         )
 
@@ -108,6 +108,7 @@ def __init__(
         client_cert_source_for_mtls: Callable[[], Tuple[bytes, bytes]] = None,
         quota_project_id=None,
         client_info: gapic_v1.client_info.ClientInfo = DEFAULT_CLIENT_INFO,
+        always_use_jwt_access: Optional[bool] = False,
     ) -> None:
         """Instantiate the transport.
 
@@ -149,6 +150,8 @@ def __init__(
                 API requests. If ``None``, then default info will be used.
                 Generally, you only need to set this if you're developing
                 your own client library.
+            always_use_jwt_access (Optional[bool]): Whether self signed JWT should
+                be used for service account credentials.
 
         Raises:
             google.auth.exceptions.MutualTlsChannelError: If mutual TLS transport
@@ -200,6 +203,7 @@ def __init__(
             scopes=scopes,
             quota_project_id=quota_project_id,
             client_info=client_info,
+            always_use_jwt_access=always_use_jwt_access,
         )
 
         if not self._grpc_channel:
diff --git a/owlbot.py b/owlbot.py
index 2281a7a8..08dd3376 100644
--- a/owlbot.py
+++ b/owlbot.py
@@ -14,12 +14,16 @@
 
 """This script is used to synthesize generated parts of this library."""
 
+import pathlib
+
 import synthtool as s
 
 from synthtool import gcp
 from synthtool.languages import python
 
 
+REPO_ROOT = pathlib.Path(__file__).parent.absolute()
+
 common = gcp.CommonTemplates()
 
 # ----------------------------------------------------------------------------
@@ -27,17 +31,12 @@
 # ----------------------------------------------------------------------------
 for library in s.get_staging_dirs("v1"):
 
-    # Comment out broken assertion in unit test
-    # https://github.com/googleapis/gapic-generator-python/issues/897
-    s.replace(
-        library / "tests/**/*.py",
-        "assert args\[0\]\.start_time == timestamp_pb2\.Timestamp\(seconds=751\)",
-        "# assert args[0].start_time == timestamp_pb2.Timestamp(seconds=751)"
-    )
+    # Fix incorrect DeprecationWarning
+    # Fixed in https://github.com/googleapis/gapic-generator-python/pull/943
     s.replace(
-        library / "tests/**/*.py",
-        "assert args\[0\]\.end_time == timestamp_pb2\.Timestamp\(seconds=751\)",
-        "# assert args[0].end_time == timestamp_pb2.Timestamp(seconds=751)"
+        "google/**/*client.py",
+        "warnings\.DeprecationWarning",
+        "DeprecationWarning"
     )
 
     s.move(library, excludes=["*.tar.gz", "docs/index.rst", "README.rst", "setup.py"])
@@ -58,3 +57,5 @@
 python.py_samples(skip_readmes=True)
 
 s.shell.run(["nox", "-s", "blacken"], hide_output=False)
+for noxfile in REPO_ROOT.glob("samples/**/noxfile.py"):
+    s.shell.run(["nox", "-s", "blacken"], cwd=noxfile.parent, hide_output=False)
diff --git a/samples/snippets/conftest.py b/samples/snippets/conftest.py
index 998d5ea7..f708ff48 100644
--- a/samples/snippets/conftest.py
+++ b/samples/snippets/conftest.py
@@ -14,6 +14,7 @@
 
 import datetime
 import os
+import random
 import uuid
 
 from google.api_core import client_options
@@ -21,9 +22,40 @@
 import google.auth
 from google.cloud import bigquery
 from google.cloud import bigquery_datatransfer
+from google.cloud import pubsub_v1
 import pytest
 
 
+RESOURCE_PREFIX = "python_bigquery_datatransfer_samples_snippets"
+RESOURCE_DATE_FORMAT = "%Y%m%d%H%M%S"
+RESOURCE_DATE_LENGTH = 4 + 2 + 2 + 2 + 2 + 2
+
+
+def resource_prefix() -> str:
+    timestamp = datetime.datetime.utcnow().strftime(RESOURCE_DATE_FORMAT)
+    random_string = hex(random.randrange(1000000))[2:]
+    return f"{RESOURCE_PREFIX}_{timestamp}_{random_string}"
+
+
+def resource_name_to_date(resource_name: str):
+    start_date = len(RESOURCE_PREFIX) + 1
+    date_string = resource_name[start_date : start_date + RESOURCE_DATE_LENGTH]
+    parsed_date = datetime.datetime.strptime(date_string, RESOURCE_DATE_FORMAT)
+    return parsed_date
+
+
+@pytest.fixture(scope="session", autouse=True)
+def cleanup_pubsub_topics(pubsub_client: pubsub_v1.PublisherClient, project_id):
+    yesterday = datetime.datetime.utcnow() - datetime.timedelta(days=1)
+    for topic in pubsub_client.list_topics(project=f"projects/{project_id}"):
+        topic_id = topic.name.split("/")[-1]
+        if (
+            topic_id.startswith(RESOURCE_PREFIX)
+            and resource_name_to_date(topic_id) < yesterday
+        ):
+            pubsub_client.delete_topic(topic=topic.name)
+
+
 def temp_suffix():
     now = datetime.datetime.now()
     return f"{now.strftime('%Y%m%d%H%M%S')}_{uuid.uuid4().hex[:8]}"
@@ -35,6 +67,21 @@ def bigquery_client(default_credentials):
     return bigquery.Client(credentials=credentials, project=project_id)
 
 
+@pytest.fixture(scope="session")
+def pubsub_client(default_credentials):
+    credentials, _ = default_credentials
+    return pubsub_v1.PublisherClient(credentials=credentials)
+
+
+@pytest.fixture(scope="session")
+def pubsub_topic(pubsub_client: pubsub_v1.PublisherClient, project_id):
+    topic_id = resource_prefix()
+    topic_path = pubsub_v1.PublisherClient.topic_path(project_id, topic_id)
+    pubsub_client.create_topic(name=topic_path)
+    yield topic_path
+    pubsub_client.delete_topic(topic=topic_path)
+
+
 @pytest.fixture(scope="session")
 def dataset_id(bigquery_client, project_id):
     dataset_id = f"bqdts_{temp_suffix()}"
@@ -56,10 +103,10 @@ def project_id():
 @pytest.fixture(scope="session")
 def service_account_name(default_credentials):
     credentials, _ = default_credentials
-    # Note: this property is not available when running with user account
-    # credentials, but only service account credentials are used in our test
-    # infrastructure.
-    return credentials.service_account_email
+    # The service_account_email attribute is not available when running with
+    # user account credentials, but should be available when running from our
+    # continuous integration tests.
+    return getattr(credentials, "service_account_email", None)
 
 
 @pytest.fixture(scope="session")
diff --git a/samples/snippets/manage_transfer_configs_test.py b/samples/snippets/manage_transfer_configs_test.py
index de31c713..52d16dc2 100644
--- a/samples/snippets/manage_transfer_configs_test.py
+++ b/samples/snippets/manage_transfer_configs_test.py
@@ -52,9 +52,7 @@ def test_update_credentials_with_service_account(
 
 def test_schedule_backfill(capsys, transfer_config_name):
     runs = manage_transfer_configs.schedule_backfill(
-        {
-            "transfer_config_name": transfer_config_name,
-        }
+        {"transfer_config_name": transfer_config_name}
     )
     out, _ = capsys.readouterr()
     assert "Started transfer runs:" in out
diff --git a/samples/snippets/noxfile.py b/samples/snippets/noxfile.py
index 5ff9e1db..b3c8658a 100644
--- a/samples/snippets/noxfile.py
+++ b/samples/snippets/noxfile.py
@@ -38,17 +38,15 @@
 
 TEST_CONFIG = {
     # You can opt out from the test for specific Python versions.
-    'ignored_versions': ["2.7"],
-
+    "ignored_versions": ["2.7"],
     # Old samples are opted out of enforcing Python type hints
     # All new samples should feature them
-    'enforce_type_hints': False,
-
+    "enforce_type_hints": False,
     # An envvar key for determining the project id to use. Change it
     # to 'BUILD_SPECIFIC_GCLOUD_PROJECT' if you want to opt in using a
     # build specific Cloud project. You can also use your own string
     # to use your own Cloud project.
-    'gcloud_project_env': 'GOOGLE_CLOUD_PROJECT',
+    "gcloud_project_env": "GOOGLE_CLOUD_PROJECT",
     # 'gcloud_project_env': 'BUILD_SPECIFIC_GCLOUD_PROJECT',
     # If you need to use a specific version of pip,
     # change pip_version_override to the string representation
@@ -56,13 +54,13 @@
     "pip_version_override": None,
     # A dictionary you want to inject into your test. Don't put any
     # secrets here. These values will override predefined values.
-    'envs': {},
+    "envs": {},
 }
 
 
 try:
     # Ensure we can import noxfile_config in the project's directory.
-    sys.path.append('.')
+    sys.path.append(".")
     from noxfile_config import TEST_CONFIG_OVERRIDE
 except ImportError as e:
     print("No user noxfile_config found: detail: {}".format(e))
@@ -77,12 +75,12 @@ def get_pytest_env_vars() -> Dict[str, str]:
     ret = {}
 
     # Override the GCLOUD_PROJECT and the alias.
-    env_key = TEST_CONFIG['gcloud_project_env']
+    env_key = TEST_CONFIG["gcloud_project_env"]
     # This should error out if not set.
-    ret['GOOGLE_CLOUD_PROJECT'] = os.environ[env_key]
+    ret["GOOGLE_CLOUD_PROJECT"] = os.environ[env_key]
 
     # Apply user supplied envs.
-    ret.update(TEST_CONFIG['envs'])
+    ret.update(TEST_CONFIG["envs"])
     return ret
 
 
@@ -91,7 +89,7 @@ def get_pytest_env_vars() -> Dict[str, str]:
 ALL_VERSIONS = ["2.7", "3.6", "3.7", "3.8", "3.9"]
 
 # Any default versions that should be ignored.
-IGNORED_VERSIONS = TEST_CONFIG['ignored_versions']
+IGNORED_VERSIONS = TEST_CONFIG["ignored_versions"]
 
 TESTED_VERSIONS = sorted([v for v in ALL_VERSIONS if v not in IGNORED_VERSIONS])
 
@@ -140,7 +138,7 @@ def _determine_local_import_names(start_dir: str) -> List[str]:
 
 @nox.session
 def lint(session: nox.sessions.Session) -> None:
-    if not TEST_CONFIG['enforce_type_hints']:
+    if not TEST_CONFIG["enforce_type_hints"]:
         session.install("flake8", "flake8-import-order")
     else:
         session.install("flake8", "flake8-import-order", "flake8-annotations")
@@ -149,9 +147,11 @@ def lint(session: nox.sessions.Session) -> None:
     args = FLAKE8_COMMON_ARGS + [
         "--application-import-names",
         ",".join(local_names),
-        "."
+        ".",
     ]
     session.run("flake8", *args)
+
+
 #
 # Black
 #
@@ -164,6 +164,7 @@ def blacken(session: nox.sessions.Session) -> None:
 
     session.run("black", *python_files)
 
+
 #
 # Sample Tests
 #
@@ -172,7 +173,9 @@ def blacken(session: nox.sessions.Session) -> None:
 PYTEST_COMMON_ARGS = ["--junitxml=sponge_log.xml"]
 
 
-def _session_tests(session: nox.sessions.Session, post_install: Callable = None) -> None:
+def _session_tests(
+    session: nox.sessions.Session, post_install: Callable = None
+) -> None:
     if TEST_CONFIG["pip_version_override"]:
         pip_version = TEST_CONFIG["pip_version_override"]
         session.install(f"pip=={pip_version}")
@@ -202,7 +205,7 @@ def _session_tests(session: nox.sessions.Session, post_install: Callable = None)
         # on travis where slow and flaky tests are excluded.
         # See http://doc.pytest.org/en/latest/_modules/_pytest/main.html
         success_codes=[0, 5],
-        env=get_pytest_env_vars()
+        env=get_pytest_env_vars(),
     )
 
 
@@ -212,9 +215,9 @@ def py(session: nox.sessions.Session) -> None:
     if session.python in TESTED_VERSIONS:
         _session_tests(session)
     else:
-        session.skip("SKIPPED: {} tests are disabled for this sample.".format(
-            session.python
-        ))
+        session.skip(
+            "SKIPPED: {} tests are disabled for this sample.".format(session.python)
+        )
 
 
 #
@@ -223,7 +226,7 @@ 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/requirements-test.txt b/samples/snippets/requirements-test.txt
index e4d022b0..e763d1e2 100644
--- a/samples/snippets/requirements-test.txt
+++ b/samples/snippets/requirements-test.txt
@@ -1,3 +1,4 @@
 google-cloud-bigquery==2.20.0
+google-cloud-pubsub==2.6.1
 pytest==6.2.4
 mock==4.0.3
diff --git a/samples/snippets/requirements.txt b/samples/snippets/requirements.txt
index 27259498..c3cb098d 100644
--- a/samples/snippets/requirements.txt
+++ b/samples/snippets/requirements.txt
@@ -1 +1 @@
-google-cloud-bigquery-datatransfer==3.1.1
+google-cloud-bigquery-datatransfer==3.2.0
diff --git a/samples/snippets/run_notification.py b/samples/snippets/run_notification.py
new file mode 100644
index 00000000..44f1bf12
--- /dev/null
+++ b/samples/snippets/run_notification.py
@@ -0,0 +1,44 @@
+# Copyright 2021 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+def run_notification(transfer_config_name, pubsub_topic):
+    orig_transfer_config_name = transfer_config_name
+    orig_pubsub_topic = pubsub_topic
+    # [START bigquerydatatransfer_run_notification]
+    transfer_config_name = "projects/1234/locations/us/transferConfigs/abcd"
+    pubsub_topic = "projects/PROJECT-ID/topics/TOPIC-ID"
+    # [END bigquerydatatransfer_run_notification]
+    transfer_config_name = orig_transfer_config_name
+    pubsub_topic = orig_pubsub_topic
+
+    # [START bigquerydatatransfer_run_notification]
+    from google.cloud import bigquery_datatransfer
+    from google.protobuf import field_mask_pb2
+
+    transfer_client = bigquery_datatransfer.DataTransferServiceClient()
+
+    transfer_config = bigquery_datatransfer.TransferConfig(name=transfer_config_name)
+    transfer_config.notification_pubsub_topic = pubsub_topic
+    update_mask = field_mask_pb2.FieldMask(paths=["notification_pubsub_topic"])
+
+    transfer_config = transfer_client.update_transfer_config(
+        {"transfer_config": transfer_config, "update_mask": update_mask}
+    )
+
+    print(f"Updated config: '{transfer_config.name}'")
+    print(f"Notification Pub/Sub topic: '{transfer_config.notification_pubsub_topic}'")
+    # [END bigquerydatatransfer_run_notification]
+    # Return the config name for testing purposes, so that it can be deleted.
+    return transfer_config
diff --git a/samples/snippets/run_notification_test.py b/samples/snippets/run_notification_test.py
new file mode 100644
index 00000000..02f24266
--- /dev/null
+++ b/samples/snippets/run_notification_test.py
@@ -0,0 +1,27 @@
+# Copyright 2021 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from . import run_notification
+
+
+def test_run_notification(capsys, transfer_config_name, pubsub_topic):
+    run_notification.run_notification(
+        transfer_config_name=transfer_config_name,
+        pubsub_topic=pubsub_topic,
+    )
+    out, _ = capsys.readouterr()
+    assert "Updated config:" in out
+    assert transfer_config_name in out
+    assert "Notification Pub/Sub topic:" in out
+    assert pubsub_topic in out
diff --git a/setup.py b/setup.py
index 043dd179..32f5cfb3 100644
--- a/setup.py
+++ b/setup.py
@@ -22,14 +22,14 @@
 
 name = "google-cloud-bigquery-datatransfer"
 description = "BigQuery Data Transfer API client library"
-version = "3.2.0"
+version = "3.3.0"
 # Should be one of:
 # 'Development Status :: 3 - Alpha'
 # 'Development Status :: 4 - Beta'
 # 'Development Status :: 5 - Production/Stable'
 release_status = "Development Status :: 5 - Production/Stable"
 dependencies = (
-    "google-api-core[grpc] >= 1.22.2, < 2.0.0dev",
+    "google-api-core[grpc] >= 1.26.0, <2.0.0dev",
     "proto-plus >= 1.15.0",
     "packaging >= 14.3",
 )
diff --git a/testing/constraints-3.6.txt b/testing/constraints-3.6.txt
index e6739c3e..d3b6361c 100644
--- a/testing/constraints-3.6.txt
+++ b/testing/constraints-3.6.txt
@@ -5,7 +5,7 @@
 #
 # e.g., if setup.py has "foo >= 1.14.0, < 2.0.0dev",
 # Then this file should have foo==1.14.0
-google-api-core==1.22.2
+google-api-core==1.26.0
 proto-plus==1.15.0
 libcst==0.2.5
 packaging==14.3
diff --git a/tests/unit/gapic/bigquery_datatransfer_v1/test_data_transfer_service.py b/tests/unit/gapic/bigquery_datatransfer_v1/test_data_transfer_service.py
index cf70ccc9..be3b2c25 100644
--- a/tests/unit/gapic/bigquery_datatransfer_v1/test_data_transfer_service.py
+++ b/tests/unit/gapic/bigquery_datatransfer_v1/test_data_transfer_service.py
@@ -41,9 +41,6 @@
 from google.cloud.bigquery_datatransfer_v1.services.data_transfer_service import (
     transports,
 )
-from google.cloud.bigquery_datatransfer_v1.services.data_transfer_service.transports.base import (
-    _API_CORE_VERSION,
-)
 from google.cloud.bigquery_datatransfer_v1.services.data_transfer_service.transports.base import (
     _GOOGLE_AUTH_VERSION,
 )
@@ -58,8 +55,9 @@
 import google.auth
 
 
-# TODO(busunkim): Once google-api-core >= 1.26.0 is required:
-# - Delete all the api-core and auth "less than" test cases
+# TODO(busunkim): Once google-auth >= 1.25.0 is required transitively
+# through google-api-core:
+# - Delete the auth "less than" test cases
 # - Delete these pytest markers (Make the "greater than or equal to" tests the default).
 requires_google_auth_lt_1_25_0 = pytest.mark.skipif(
     packaging.version.parse(_GOOGLE_AUTH_VERSION) >= packaging.version.parse("1.25.0"),
@@ -70,16 +68,6 @@
     reason="This test requires google-auth >= 1.25.0",
 )
 
-requires_api_core_lt_1_26_0 = pytest.mark.skipif(
-    packaging.version.parse(_API_CORE_VERSION) >= packaging.version.parse("1.26.0"),
-    reason="This test requires google-api-core < 1.26.0",
-)
-
-requires_api_core_gte_1_26_0 = pytest.mark.skipif(
-    packaging.version.parse(_API_CORE_VERSION) < packaging.version.parse("1.26.0"),
-    reason="This test requires google-api-core >= 1.26.0",
-)
-
 
 def client_cert_source_callback():
     return b"cert bytes", b"key bytes"
@@ -143,6 +131,36 @@ def test_data_transfer_service_client_from_service_account_info(client_class):
         assert client.transport._host == "bigquerydatatransfer.googleapis.com:443"
 
 
+@pytest.mark.parametrize(
+    "client_class", [DataTransferServiceClient, DataTransferServiceAsyncClient,]
+)
+def test_data_transfer_service_client_service_account_always_use_jwt(client_class):
+    with mock.patch.object(
+        service_account.Credentials, "with_always_use_jwt_access", create=True
+    ) as use_jwt:
+        creds = service_account.Credentials(None, None, None)
+        client = client_class(credentials=creds)
+        use_jwt.assert_not_called()
+
+
+@pytest.mark.parametrize(
+    "transport_class,transport_name",
+    [
+        (transports.DataTransferServiceGrpcTransport, "grpc"),
+        (transports.DataTransferServiceGrpcAsyncIOTransport, "grpc_asyncio"),
+    ],
+)
+def test_data_transfer_service_client_service_account_always_use_jwt_true(
+    transport_class, transport_name
+):
+    with mock.patch.object(
+        service_account.Credentials, "with_always_use_jwt_access", create=True
+    ) as use_jwt:
+        creds = service_account.Credentials(None, None, None)
+        transport = transport_class(credentials=creds, always_use_jwt_access=True)
+        use_jwt.assert_called_once_with(True)
+
+
 @pytest.mark.parametrize(
     "client_class", [DataTransferServiceClient, DataTransferServiceAsyncClient,]
 )
@@ -2776,8 +2794,12 @@ def test_schedule_transfer_runs_flattened():
         assert len(call.mock_calls) == 1
         _, args, _ = call.mock_calls[0]
         assert args[0].parent == "parent_value"
-        # assert args[0].start_time == timestamp_pb2.Timestamp(seconds=751)
-        # assert args[0].end_time == timestamp_pb2.Timestamp(seconds=751)
+        assert TimestampRule().to_proto(args[0].start_time) == timestamp_pb2.Timestamp(
+            seconds=751
+        )
+        assert TimestampRule().to_proto(args[0].end_time) == timestamp_pb2.Timestamp(
+            seconds=751
+        )
 
 
 def test_schedule_transfer_runs_flattened_error():
@@ -2825,8 +2847,12 @@ async def test_schedule_transfer_runs_flattened_async():
         assert len(call.mock_calls)
         _, args, _ = call.mock_calls[0]
         assert args[0].parent == "parent_value"
-        # assert args[0].start_time == timestamp_pb2.Timestamp(seconds=751)
-        # assert args[0].end_time == timestamp_pb2.Timestamp(seconds=751)
+        assert TimestampRule().to_proto(args[0].start_time) == timestamp_pb2.Timestamp(
+            seconds=751
+        )
+        assert TimestampRule().to_proto(args[0].end_time) == timestamp_pb2.Timestamp(
+            seconds=751
+        )
 
 
 @pytest.mark.asyncio
@@ -4684,7 +4710,6 @@ def test_data_transfer_service_transport_auth_adc_old_google_auth(transport_clas
         (transports.DataTransferServiceGrpcAsyncIOTransport, grpc_helpers_async),
     ],
 )
-@requires_api_core_gte_1_26_0
 def test_data_transfer_service_transport_create_channel(transport_class, grpc_helpers):
     # If credentials and host are not provided, the transport class should use
     # ADC credentials.
@@ -4713,79 +4738,6 @@ def test_data_transfer_service_transport_create_channel(transport_class, grpc_he
         )
 
 
-@pytest.mark.parametrize(
-    "transport_class,grpc_helpers",
-    [
-        (transports.DataTransferServiceGrpcTransport, grpc_helpers),
-        (transports.DataTransferServiceGrpcAsyncIOTransport, grpc_helpers_async),
-    ],
-)
-@requires_api_core_lt_1_26_0
-def test_data_transfer_service_transport_create_channel_old_api_core(
-    transport_class, grpc_helpers
-):
-    # If credentials and host are not provided, the transport class should use
-    # ADC credentials.
-    with mock.patch.object(
-        google.auth, "default", autospec=True
-    ) as adc, mock.patch.object(
-        grpc_helpers, "create_channel", autospec=True
-    ) as create_channel:
-        creds = ga_credentials.AnonymousCredentials()
-        adc.return_value = (creds, None)
-        transport_class(quota_project_id="octopus")
-
-        create_channel.assert_called_with(
-            "bigquerydatatransfer.googleapis.com:443",
-            credentials=creds,
-            credentials_file=None,
-            quota_project_id="octopus",
-            scopes=("https://www.googleapis.com/auth/cloud-platform",),
-            ssl_credentials=None,
-            options=[
-                ("grpc.max_send_message_length", -1),
-                ("grpc.max_receive_message_length", -1),
-            ],
-        )
-
-
-@pytest.mark.parametrize(
-    "transport_class,grpc_helpers",
-    [
-        (transports.DataTransferServiceGrpcTransport, grpc_helpers),
-        (transports.DataTransferServiceGrpcAsyncIOTransport, grpc_helpers_async),
-    ],
-)
-@requires_api_core_lt_1_26_0
-def test_data_transfer_service_transport_create_channel_user_scopes(
-    transport_class, grpc_helpers
-):
-    # If credentials and host are not provided, the transport class should use
-    # ADC credentials.
-    with mock.patch.object(
-        google.auth, "default", autospec=True
-    ) as adc, mock.patch.object(
-        grpc_helpers, "create_channel", autospec=True
-    ) as create_channel:
-        creds = ga_credentials.AnonymousCredentials()
-        adc.return_value = (creds, None)
-
-        transport_class(quota_project_id="octopus", scopes=["1", "2"])
-
-        create_channel.assert_called_with(
-            "bigquerydatatransfer.googleapis.com:443",
-            credentials=creds,
-            credentials_file=None,
-            quota_project_id="octopus",
-            scopes=["1", "2"],
-            ssl_credentials=None,
-            options=[
-                ("grpc.max_send_message_length", -1),
-                ("grpc.max_receive_message_length", -1),
-            ],
-        )
-
-
 @pytest.mark.parametrize(
     "transport_class",
     [
@@ -4810,7 +4762,7 @@ def test_data_transfer_service_grpc_transport_client_cert_source_for_mtls(
             "squid.clam.whelk:443",
             credentials=cred,
             credentials_file=None,
-            scopes=("https://www.googleapis.com/auth/cloud-platform",),
+            scopes=None,
             ssl_credentials=mock_ssl_channel_creds,
             quota_project_id=None,
             options=[
@@ -4919,7 +4871,7 @@ def test_data_transfer_service_transport_channel_mtls_with_client_cert_source(
                 "mtls.squid.clam.whelk:443",
                 credentials=cred,
                 credentials_file=None,
-                scopes=("https://www.googleapis.com/auth/cloud-platform",),
+                scopes=None,
                 ssl_credentials=mock_ssl_cred,
                 quota_project_id=None,
                 options=[
@@ -4966,7 +4918,7 @@ def test_data_transfer_service_transport_channel_mtls_with_adc(transport_class):
                 "mtls.squid.clam.whelk:443",
                 credentials=mock_cred,
                 credentials_file=None,
-                scopes=("https://www.googleapis.com/auth/cloud-platform",),
+                scopes=None,
                 ssl_credentials=mock_ssl_cred,
                 quota_project_id=None,
                 options=[