test: add tests for lazy imports in gapic_v1

Author: hebaalazzeh

packages/google-api-core/tests/unit/gapic/test_lazy_imports.py

@@ -0,0 +1,87 @@
+# Copyright 2026 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.
+
+import subprocess
+import sys
+
+import pytest
+
+SCRIPT_PYTHON_315 = """
+import sys
+import google.api_core.gapic_v1
+
+# The inner gapic_v1 modules should NOT be loaded yet
+HEAVY_MODULES = [
+    "google.api_core.gapic_v1.client_info",
+    "google.api_core.gapic_v1.config",
+    "google.api_core.gapic_v1.config_async",
+    "google.api_core.gapic_v1.method",
+    "google.api_core.gapic_v1.method_async",
+    "google.api_core.gapic_v1.routing_header",
+]
+
+for mod in HEAVY_MODULES:
+    if mod in sys.modules:
+        print(f"FAILED: {mod} was eagerly loaded into sys.modules")
+        sys.exit(1)
+
+# Trigger reification
+import google.api_core.gapic_v1.client_info
+_ = google.api_core.gapic_v1.client_info.__name__
+
+if "google.api_core.gapic_v1.client_info" not in sys.modules:
+    print("FAILED: google.api_core.gapic_v1.client_info was not lazily loaded upon access")
+    sys.exit(2)
+
+sys.exit(0)
+"""
+
+SCRIPT_PRE_315 = """
+import sys
+import google.api_core.gapic_v1
+
+HEAVY_MODULES = [
+    "google.api_core.gapic_v1.client_info",
+    "google.api_core.gapic_v1.config",
+    "google.api_core.gapic_v1.config_async",
+    "google.api_core.gapic_v1.method",
+    "google.api_core.gapic_v1.method_async",
+    "google.api_core.gapic_v1.routing_header",
+]
+
+for mod in HEAVY_MODULES:
+    if mod not in sys.modules:
+        print(f"FAILED: {mod} was not eagerly loaded into sys.modules")
+        sys.exit(1)
+
+sys.exit(0)
+"""
+
+
+@pytest.mark.skipif(sys.version_info < (3, 15), reason="PEP 810 requires Python 3.15+")
+def test_lazy_imports_on_python_315():
+    result = subprocess.run(
+        [sys.executable, "-c", SCRIPT_PYTHON_315], capture_output=True, text=True
+    )
+    assert result.returncode == 0, f"Subprocess failed: {result.stdout}"
+
+
+@pytest.mark.skipif(
+    sys.version_info >= (3, 15), reason="Testing fallback behavior on < 3.15"
+)
+def test_fallback_eager_imports_pre_315():
+    result = subprocess.run(
+        [sys.executable, "-c", SCRIPT_PRE_315], capture_output=True, text=True
+    )
+    assert result.returncode == 0, f"Subprocess failed: {result.stdout}"