fix: Switch to unittest.mock from mock (#713)

* test: Switch to unittest.mock from mock

Now that the minimum supported version of Python is 3.7, we can stop
using the external mock requirement, and import it from unittest. I have
also attempted to keep imports ordered.

Fixes #377

* test: Fallback to external mock for AsyncMock

AsyncMock is not included in unittest.mock under Python 3.7, so we must
fallback to the external mock requirement for that Python version. Only
install it for that version.

Keep this as a separate commit so it can be reverted when 3.7 isn't
supported anymore.

* lint

* clean up to satisfy mypy

* lint

* fix build

---------

Co-authored-by: Anthonios Partheniou <partheniou@google.com>

Author: s-t-e-v-e-n-k

packages/google-api-core/noxfile.py

@@ -124,7 +124,7 @@ def default(session, install_grpc=True, prerelease=False, install_async_rest=Fal
 
     session.install(
         "dataclasses",
-        "mock",
+        "mock; python_version=='3.7'",
         "pytest",
         "pytest-cov",
         "pytest-xdist",
@@ -280,8 +280,8 @@ def mypy(session):
         "types-setuptools",
         "types-requests",
         "types-protobuf",
-        "types-mock",
         "types-dataclasses",
+        "types-mock; python_version=='3.7'",
     )
     session.run("mypy", "google", "tests")
 

packages/google-api-core/tests/asyncio/future/test_async_future.py

@@ -13,8 +13,8 @@
 # limitations under the License.
 
 import asyncio
+from unittest import mock
 
-import mock
 import pytest
 
 from google.api_core import exceptions

packages/google-api-core/tests/asyncio/gapic/test_method_async.py

@@ -14,7 +14,11 @@
 
 import datetime
 
-import mock
+try:
+    from unittest import mock
+    from unittest.mock import AsyncMock  # pragma: NO COVER  # noqa: F401
+except ImportError:  # pragma: NO COVER
+    import mock  # type: ignore
 import pytest
 
 try:

packages/google-api-core/tests/asyncio/operations_v1/test_operations_async_client.py

@@ -12,7 +12,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import mock
+from unittest import mock
+
 import pytest
 
 try:

packages/google-api-core/tests/asyncio/retry/test_retry_streaming_async.py

@@ -12,11 +12,16 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import asyncio
 import datetime
 import re
-import asyncio
 
-import mock
+try:
+    from unittest import mock
+    from unittest.mock import AsyncMock  # pragma: NO COVER  # noqa: F401
+except ImportError:  # pragma: NO COVER
+    import mock  # type: ignore
+
 import pytest
 
 from google.api_core import exceptions

packages/google-api-core/tests/asyncio/retry/test_retry_unary_async.py

@@ -15,7 +15,11 @@
 import datetime
 import re
 
-import mock
+try:
+    from unittest import mock
+    from unittest.mock import AsyncMock  # pragma: NO COVER  # noqa: F401
+except ImportError:  # pragma: NO COVER
+    import mock  # type: ignore
 import pytest
 
 from google.api_core import exceptions

packages/google-api-core/tests/asyncio/test_grpc_helpers_async.py

@@ -12,7 +12,11 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import mock
+try:
+    from unittest import mock
+    from unittest.mock import AsyncMock  # pragma: NO COVER  # noqa: F401
+except ImportError:  # pragma: NO COVER
+    import mock  # type: ignore
 import pytest  # noqa: I202
 
 try:

packages/google-api-core/tests/asyncio/test_operation_async.py

@@ -13,9 +13,14 @@
 # limitations under the License.
 
 
-import mock
 import pytest
 
+try:
+    from unittest import mock
+    from unittest.mock import AsyncMock  # pragma: NO COVER  # noqa: F401
+except ImportError:  # pragma: NO COVER
+    import mock  # type: ignore
+
 try:
     import grpc  # noqa: F401
 except ImportError:  # pragma: NO COVER

packages/google-api-core/tests/asyncio/test_page_iterator_async.py

@@ -14,7 +14,11 @@
 
 import inspect
 
-import mock
+try:
+    from unittest import mock
+    from unittest.mock import AsyncMock  # pragma: NO COVER  # noqa: F401
+except ImportError:  # pragma: NO COVER
+    import mock  # type: ignore
 import pytest
 
 from google.api_core import page_iterator_async

packages/google-api-core/tests/asyncio/test_rest_streaming_async.py

@@ -15,15 +15,20 @@
 # TODO: set random.seed explicitly in each test function.
 # See related issue: https://github.com/googleapis/python-api-core/issues/689.
 
-import pytest  # noqa: I202
-import mock
-
 import datetime
 import logging
 import random
 import time
 from typing import List, AsyncIterator
 
+try:
+    from unittest import mock
+    from unittest.mock import AsyncMock  # pragma: NO COVER  # noqa: F401
+except ImportError:  # pragma: NO COVER
+    import mock  # type: ignore
+
+import pytest  # noqa: I202
+
 import proto
 
 try: