diff --git a/gapic/templates/noxfile.py.j2 b/gapic/templates/noxfile.py.j2
index 6408f306dc..d8b637b332 100644
--- a/gapic/templates/noxfile.py.j2
+++ b/gapic/templates/noxfile.py.j2
@@ -55,6 +55,7 @@ SYSTEM_TEST_PYTHON_VERSIONS: List[str] = ["3.8", "3.9", "3.10", "3.11", "3.12",
 SYSTEM_TEST_STANDARD_DEPENDENCIES = [
     "mock",
     "pytest",
+    "pytest-asyncio"
     "google-cloud-testutils",
 ]
 SYSTEM_TEST_EXTERNAL_DEPENDENCIES: List[str] = []
@@ -81,7 +82,8 @@ nox.options.error_on_missing_interpreters = True
 def mypy(session):
     """Run the type checker."""
     session.install(
-        "mypy",
+        # TODO(https://github.com/googleapis/gapic-generator-python/issues/2410): Use the latest version of mypy
+        "mypy<1.16.0",
         "types-requests",
         "types-protobuf",
     )
diff --git a/gapic/templates/tests/unit/gapic/%name_%version/%sub/test_%service.py.j2 b/gapic/templates/tests/unit/gapic/%name_%version/%sub/test_%service.py.j2
index a69026767c..92fa506b56 100644
--- a/gapic/templates/tests/unit/gapic/%name_%version/%sub/test_%service.py.j2
+++ b/gapic/templates/tests/unit/gapic/%name_%version/%sub/test_%service.py.j2
@@ -226,6 +226,7 @@ def test__get_api_endpoint():
 {% for method in service.methods.values() %}{% with method_name = method.name|snake_case %}
 {% for mode in ["", "async"] %}
 {% if mode == "async" %}
+@pytest.mark.asyncio
 async def test_{{ method_name }}_api_version_header_async(transport_name="grpc"):
     client = {{ service.async_client_name }}(credentials=async_anonymous_credentials(), transport=transport_name)
 {% else %}
@@ -247,8 +248,8 @@ def test_{{ method_name }}_api_version_header(transport_name):
         # Mock the actual call within the gRPC stub, and fake the request.
         with mock.patch.object(
                 type(client.transport.{{ method.transport_safe_name|snake_case }}),
-                '__call__'
-            ) as call:
+                '__call__'{% if mode == "async" %},
+                new_callable=AsyncMock{% endif %}) as call:
             {% if mode == "async" %}
                 await client.{{ method_name }}()
             {% else %}
diff --git a/noxfile.py b/noxfile.py
index 7b686cb7db..2d688e139b 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -392,9 +392,9 @@ def showcase(
     """Run the Showcase test suite."""
 
     with showcase_library(session, templates=templates, other_opts=other_opts):
-        # Exclude pytest-asyncio==1.0.0 while we investigate the recent failure described in
+        # Use pytest-asyncio<1.0.0 while we investigate the recent failure described in
         # https://github.com/googleapis/gapic-generator-python/issues/2399
-        session.install("pytest", "pytest-asyncio!=1.0.0")
+        session.install("pytest", "pytest-asyncio<1.0.0")
         test_directory = Path("tests", "system")
         ignore_file = env.get("IGNORE_FILE")
         pytest_command = [
@@ -424,9 +424,9 @@ def showcase_w_rest_async(
     with showcase_library(
         session, templates=templates, other_opts=other_opts, rest_async_io_enabled=True
     ):
-        # Exclude pytest-asyncio==1.0.0 while we investigate the recent failure described in
+        # Use pytest-asyncio<1.0.0 while we investigate the recent failure described in
         # https://github.com/googleapis/gapic-generator-python/issues/2399
-        session.install("pytest", "pytest-asyncio!=1.0.0")
+        session.install("pytest", "pytest-asyncio<1.0.0")
         test_directory = Path("tests", "system")
         ignore_file = env.get("IGNORE_FILE")
         pytest_command = [
@@ -589,7 +589,8 @@ def showcase_mypy(
     """Perform typecheck analysis on the generated Showcase library."""
 
     session.install(
-        "mypy",
+        # TODO(https://github.com/googleapis/gapic-generator-python/issues/2410): Use the latest version of mypy
+        "mypy<1.16.0",
         "types-setuptools",
         "types-protobuf",
         "types-requests",
diff --git a/tests/integration/goldens/asset/noxfile.py b/tests/integration/goldens/asset/noxfile.py
index 4efb1b1161..cd82d70fc3 100755
--- a/tests/integration/goldens/asset/noxfile.py
+++ b/tests/integration/goldens/asset/noxfile.py
@@ -62,6 +62,7 @@
 SYSTEM_TEST_STANDARD_DEPENDENCIES = [
     "mock",
     "pytest",
+    "pytest-asyncio"
     "google-cloud-testutils",
 ]
 SYSTEM_TEST_EXTERNAL_DEPENDENCIES: List[str] = []
@@ -88,7 +89,8 @@
 def mypy(session):
     """Run the type checker."""
     session.install(
-        "mypy",
+        # TODO(https://github.com/googleapis/gapic-generator-python/issues/2410): Use the latest version of mypy
+        "mypy<1.16.0",
         "types-requests",
         "types-protobuf",
     )
diff --git a/tests/integration/goldens/credentials/noxfile.py b/tests/integration/goldens/credentials/noxfile.py
index 3aea2c0c1b..b8d69efb62 100755
--- a/tests/integration/goldens/credentials/noxfile.py
+++ b/tests/integration/goldens/credentials/noxfile.py
@@ -62,6 +62,7 @@
 SYSTEM_TEST_STANDARD_DEPENDENCIES = [
     "mock",
     "pytest",
+    "pytest-asyncio"
     "google-cloud-testutils",
 ]
 SYSTEM_TEST_EXTERNAL_DEPENDENCIES: List[str] = []
@@ -88,7 +89,8 @@
 def mypy(session):
     """Run the type checker."""
     session.install(
-        "mypy",
+        # TODO(https://github.com/googleapis/gapic-generator-python/issues/2410): Use the latest version of mypy
+        "mypy<1.16.0",
         "types-requests",
         "types-protobuf",
     )
diff --git a/tests/integration/goldens/eventarc/noxfile.py b/tests/integration/goldens/eventarc/noxfile.py
index ba8fbf5fc2..4d16eb8942 100755
--- a/tests/integration/goldens/eventarc/noxfile.py
+++ b/tests/integration/goldens/eventarc/noxfile.py
@@ -62,6 +62,7 @@
 SYSTEM_TEST_STANDARD_DEPENDENCIES = [
     "mock",
     "pytest",
+    "pytest-asyncio"
     "google-cloud-testutils",
 ]
 SYSTEM_TEST_EXTERNAL_DEPENDENCIES: List[str] = []
@@ -88,7 +89,8 @@
 def mypy(session):
     """Run the type checker."""
     session.install(
-        "mypy",
+        # TODO(https://github.com/googleapis/gapic-generator-python/issues/2410): Use the latest version of mypy
+        "mypy<1.16.0",
         "types-requests",
         "types-protobuf",
     )
diff --git a/tests/integration/goldens/logging/noxfile.py b/tests/integration/goldens/logging/noxfile.py
index 2e9dd52f17..9b3a46d3f6 100755
--- a/tests/integration/goldens/logging/noxfile.py
+++ b/tests/integration/goldens/logging/noxfile.py
@@ -62,6 +62,7 @@
 SYSTEM_TEST_STANDARD_DEPENDENCIES = [
     "mock",
     "pytest",
+    "pytest-asyncio"
     "google-cloud-testutils",
 ]
 SYSTEM_TEST_EXTERNAL_DEPENDENCIES: List[str] = []
@@ -88,7 +89,8 @@
 def mypy(session):
     """Run the type checker."""
     session.install(
-        "mypy",
+        # TODO(https://github.com/googleapis/gapic-generator-python/issues/2410): Use the latest version of mypy
+        "mypy<1.16.0",
         "types-requests",
         "types-protobuf",
     )
diff --git a/tests/integration/goldens/logging_internal/noxfile.py b/tests/integration/goldens/logging_internal/noxfile.py
index 2e9dd52f17..9b3a46d3f6 100755
--- a/tests/integration/goldens/logging_internal/noxfile.py
+++ b/tests/integration/goldens/logging_internal/noxfile.py
@@ -62,6 +62,7 @@
 SYSTEM_TEST_STANDARD_DEPENDENCIES = [
     "mock",
     "pytest",
+    "pytest-asyncio"
     "google-cloud-testutils",
 ]
 SYSTEM_TEST_EXTERNAL_DEPENDENCIES: List[str] = []
@@ -88,7 +89,8 @@
 def mypy(session):
     """Run the type checker."""
     session.install(
-        "mypy",
+        # TODO(https://github.com/googleapis/gapic-generator-python/issues/2410): Use the latest version of mypy
+        "mypy<1.16.0",
         "types-requests",
         "types-protobuf",
     )
diff --git a/tests/integration/goldens/redis/noxfile.py b/tests/integration/goldens/redis/noxfile.py
index 5768044661..788cc456f6 100755
--- a/tests/integration/goldens/redis/noxfile.py
+++ b/tests/integration/goldens/redis/noxfile.py
@@ -62,6 +62,7 @@
 SYSTEM_TEST_STANDARD_DEPENDENCIES = [
     "mock",
     "pytest",
+    "pytest-asyncio"
     "google-cloud-testutils",
 ]
 SYSTEM_TEST_EXTERNAL_DEPENDENCIES: List[str] = []
@@ -88,7 +89,8 @@
 def mypy(session):
     """Run the type checker."""
     session.install(
-        "mypy",
+        # TODO(https://github.com/googleapis/gapic-generator-python/issues/2410): Use the latest version of mypy
+        "mypy<1.16.0",
         "types-requests",
         "types-protobuf",
     )
diff --git a/tests/integration/goldens/redis_selective/noxfile.py b/tests/integration/goldens/redis_selective/noxfile.py
index 5768044661..788cc456f6 100755
--- a/tests/integration/goldens/redis_selective/noxfile.py
+++ b/tests/integration/goldens/redis_selective/noxfile.py
@@ -62,6 +62,7 @@
 SYSTEM_TEST_STANDARD_DEPENDENCIES = [
     "mock",
     "pytest",
+    "pytest-asyncio"
     "google-cloud-testutils",
 ]
 SYSTEM_TEST_EXTERNAL_DEPENDENCIES: List[str] = []
@@ -88,7 +89,8 @@
 def mypy(session):
     """Run the type checker."""
     session.install(
-        "mypy",
+        # TODO(https://github.com/googleapis/gapic-generator-python/issues/2410): Use the latest version of mypy
+        "mypy<1.16.0",
         "types-requests",
         "types-protobuf",
     )