test: fix hanging resource limits test with proper mocking

The `test_resource_limits_set` unit test was previously setting resource limits (such as a 100MB memory cap) on the test runner process itself, rather than the isolated subprocess. This caused the CI runner (e.g., GitHub Actions) to starve for resources and hang or crash.

This change fixes the issue by scoping the `setrlimit` mock correctly and adds a safety mechanism to prevent future regressions from bringing down CI.

Co-authored-by: Liang Wu <wuliang@google.com>
PiperOrigin-RevId: 895565166

Author: wuliang229

tests/unittests/tools/test_bash_tool.py

@@ -263,13 +263,25 @@ async def test_resource_limits_set(self, workspace, tool_context_confirmed):
       assert "preexec_fn" in mock_exec.call_args.kwargs
       preexec_fn = mock_exec.call_args.kwargs["preexec_fn"]
 
-      mock_setrlimit = mock.create_autospec(resource.setrlimit, instance=True)
-      with mock.patch("resource.setrlimit", mock_setrlimit):
+      # Save current limits to detect if the real process is modified
+      orig_as = resource.getrlimit(resource.RLIMIT_AS)
+
+      with mock.patch(
+          "google.adk.tools.bash_tool.resource.setrlimit"
+      ) as mock_setrlimit:
         preexec_fn()
-        mock_setrlimit.assert_any_call(resource.RLIMIT_CORE, (0, 0))
-        mock_setrlimit.assert_any_call(
-            resource.RLIMIT_AS, (100 * 1024 * 1024, 100 * 1024 * 1024)
-        )
-        mock_setrlimit.assert_any_call(
-            resource.RLIMIT_FSIZE, (50 * 1024 * 1024, 50 * 1024 * 1024)
-        )
+
+      # Check if process limits were accidentally modified (leaked)
+      current_as = resource.getrlimit(resource.RLIMIT_AS)
+      if current_as != orig_as:
+        # Reset to prevent environment corruption
+        resource.setrlimit(resource.RLIMIT_AS, orig_as)
+        pytest.fail("Test modified process resource limits! Mocking failed.")
+
+      mock_setrlimit.assert_any_call(resource.RLIMIT_CORE, (0, 0))
+      mock_setrlimit.assert_any_call(
+          resource.RLIMIT_AS, (100 * 1024 * 1024, 100 * 1024 * 1024)
+      )
+      mock_setrlimit.assert_any_call(
+          resource.RLIMIT_FSIZE, (50 * 1024 * 1024, 50 * 1024 * 1024)
+      )