diff -up ./tests/asyncio/future/test_async_future.py.orig ./tests/asyncio/future/test_async_future.py
--- ./tests/asyncio/future/test_async_future.py.orig	2021-08-23 07:02:16.988893673 -0500
+++ ./tests/asyncio/future/test_async_future.py	2021-08-23 07:05:20.264433127 -0500
@@ -14,7 +14,7 @@
 
 import asyncio
 
-import mock
+from unittest import mock
 import pytest
 
 from google.api_core import exceptions
diff -up ./tests/asyncio/gapic/test_method_async.py.orig ./tests/asyncio/gapic/test_method_async.py
--- ./tests/asyncio/gapic/test_method_async.py.orig	2021-08-23 07:02:16.988893673 -0500
+++ ./tests/asyncio/gapic/test_method_async.py	2021-08-23 07:05:20.265433119 -0500
@@ -15,7 +15,7 @@
 import datetime
 
 from grpc import aio
-import mock
+from unittest import mock
 import pytest
 
 from google.api_core import exceptions
diff -up ./tests/asyncio/operations_v1/test_operations_async_client.py.orig ./tests/asyncio/operations_v1/test_operations_async_client.py
--- ./tests/asyncio/operations_v1/test_operations_async_client.py.orig	2021-08-23 07:02:16.988893673 -0500
+++ ./tests/asyncio/operations_v1/test_operations_async_client.py	2021-08-23 07:05:20.265433119 -0500
@@ -13,7 +13,7 @@
 # limitations under the License.
 
 from grpc import aio
-import mock
+from unittest import mock
 import pytest
 
 from google.api_core import grpc_helpers_async, operations_v1, page_iterator_async
diff -up ./tests/asyncio/test_grpc_helpers_async.py.orig ./tests/asyncio/test_grpc_helpers_async.py
--- ./tests/asyncio/test_grpc_helpers_async.py.orig	2021-08-23 07:02:16.988893673 -0500
+++ ./tests/asyncio/test_grpc_helpers_async.py	2021-08-23 07:05:20.265433119 -0500
@@ -14,7 +14,7 @@
 
 import grpc
 from grpc import aio
-import mock
+from unittest import mock
 import pytest
 
 from google.api_core import exceptions
diff -up ./tests/asyncio/test_operation_async.py.orig ./tests/asyncio/test_operation_async.py
--- ./tests/asyncio/test_operation_async.py.orig	2021-08-23 07:02:16.988893673 -0500
+++ ./tests/asyncio/test_operation_async.py	2021-08-23 07:05:20.266433111 -0500
@@ -13,7 +13,7 @@
 # limitations under the License.
 
 
-import mock
+from unittest import mock
 import pytest
 
 from google.api_core import exceptions
diff -up ./tests/asyncio/test_page_iterator_async.py.orig ./tests/asyncio/test_page_iterator_async.py
--- ./tests/asyncio/test_page_iterator_async.py.orig	2021-08-23 07:02:16.988893673 -0500
+++ ./tests/asyncio/test_page_iterator_async.py	2021-08-23 07:05:20.266433111 -0500
@@ -14,7 +14,7 @@
 
 import inspect
 
-import mock
+from unittest import mock
 import pytest
 
 from google.api_core import page_iterator_async
diff -up ./tests/asyncio/test_retry_async.py.orig ./tests/asyncio/test_retry_async.py
--- ./tests/asyncio/test_retry_async.py.orig	2021-08-23 07:02:16.989893665 -0500
+++ ./tests/asyncio/test_retry_async.py	2021-08-23 07:05:20.267433103 -0500
@@ -15,7 +15,7 @@
 import datetime
 import re
 
-import mock
+from unittest import mock
 import pytest
 
 from google.api_core import exceptions
diff -up ./tests/unit/future/test__helpers.py.orig ./tests/unit/future/test__helpers.py
--- ./tests/unit/future/test__helpers.py.orig	2021-08-23 07:02:16.989893665 -0500
+++ ./tests/unit/future/test__helpers.py	2021-08-23 07:05:20.267433103 -0500
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import mock
+from unittest import mock
 
 from google.api_core.future import _helpers
 
diff -up ./tests/unit/future/test_polling.py.orig ./tests/unit/future/test_polling.py
--- ./tests/unit/future/test_polling.py.orig	2021-08-23 07:02:16.989893665 -0500
+++ ./tests/unit/future/test_polling.py	2021-08-23 07:05:20.268433095 -0500
@@ -16,7 +16,7 @@ import concurrent.futures
 import threading
 import time
 
-import mock
+from unittest import mock
 import pytest
 
 from google.api_core import exceptions, retry
diff -up ./tests/unit/gapic/test_method.py.orig ./tests/unit/gapic/test_method.py
--- ./tests/unit/gapic/test_method.py.orig	2021-08-23 07:02:16.989893665 -0500
+++ ./tests/unit/gapic/test_method.py	2021-08-23 07:05:20.268433095 -0500
@@ -14,7 +14,7 @@
 
 import datetime
 
-import mock
+from unittest import mock
 
 from google.api_core import exceptions
 from google.api_core import retry
diff -up ./tests/unit/test_bidi.py.orig ./tests/unit/test_bidi.py
--- ./tests/unit/test_bidi.py.orig	2021-08-23 07:02:16.989893665 -0500
+++ ./tests/unit/test_bidi.py	2021-08-23 07:05:20.269433087 -0500
@@ -18,7 +18,7 @@ import queue
 import threading
 
 import grpc
-import mock
+from unittest import mock
 import pytest
 
 from google.api_core import bidi
diff -up ./tests/unit/test_exceptions.py.orig ./tests/unit/test_exceptions.py
--- ./tests/unit/test_exceptions.py.orig	2021-08-23 07:02:16.990893657 -0500
+++ ./tests/unit/test_exceptions.py	2021-08-23 07:05:20.269433087 -0500
@@ -16,7 +16,7 @@ import http.client
 import json
 
 import grpc
-import mock
+from unittest import mock
 import requests
 
 from google.api_core import exceptions
diff -up ./tests/unit/test_grpc_helpers.py.orig ./tests/unit/test_grpc_helpers.py
--- ./tests/unit/test_grpc_helpers.py.orig	2021-08-23 07:02:16.990893657 -0500
+++ ./tests/unit/test_grpc_helpers.py	2021-08-23 07:05:20.270433079 -0500
@@ -13,7 +13,7 @@
 # limitations under the License.
 
 import grpc
-import mock
+from unittest import mock
 import pytest
 
 from google.api_core import exceptions
diff -up ./tests/unit/test_operation.py.orig ./tests/unit/test_operation.py
--- ./tests/unit/test_operation.py.orig	2021-08-23 07:02:16.990893657 -0500
+++ ./tests/unit/test_operation.py	2021-08-23 07:05:20.270433079 -0500
@@ -13,7 +13,7 @@
 # limitations under the License.
 
 
-import mock
+from unittest import mock
 
 from google.api_core import exceptions
 from google.api_core import operation
diff -up ./tests/unit/test_page_iterator.py.orig ./tests/unit/test_page_iterator.py
--- ./tests/unit/test_page_iterator.py.orig	2021-08-23 07:02:16.990893657 -0500
+++ ./tests/unit/test_page_iterator.py	2021-08-23 07:05:20.271433071 -0500
@@ -15,7 +15,7 @@
 import math
 import types
 
-import mock
+from unittest import mock
 import pytest
 
 from google.api_core import page_iterator
diff -up ./tests/unit/test_path_template.py.orig ./tests/unit/test_path_template.py
--- ./tests/unit/test_path_template.py.orig	2021-08-23 07:02:16.990893657 -0500
+++ ./tests/unit/test_path_template.py	2021-08-23 07:05:20.271433071 -0500
@@ -14,7 +14,7 @@
 
 from __future__ import unicode_literals
 
-import mock
+from unittest import mock
 import pytest
 
 from google.api_core import path_template
diff -up ./tests/unit/test_retry.py.orig ./tests/unit/test_retry.py
--- ./tests/unit/test_retry.py.orig	2021-08-23 07:02:16.990893657 -0500
+++ ./tests/unit/test_retry.py	2021-08-23 07:05:20.272433063 -0500
@@ -16,7 +16,7 @@ import datetime
 import itertools
 import re
 
-import mock
+from unittest import mock
 import pytest
 import requests.exceptions
 
diff -up ./tests/unit/test_timeout.py.orig ./tests/unit/test_timeout.py
--- ./tests/unit/test_timeout.py.orig	2021-08-23 07:02:16.990893657 -0500
+++ ./tests/unit/test_timeout.py	2021-08-23 07:05:20.273433055 -0500
@@ -15,7 +15,7 @@
 import datetime
 import itertools
 
-import mock
+from unittest import mock
 
 from google.api_core import timeout