Restrict take_event deadlock test to fastrtps and skip when not exercised

The test was registered for every rmw implementation via
call_for_each_rmw_implementation(test_api). On non-fastrtps stacks
FASTRTPS_DEFAULT_PROFILES_FILE is a no-op and a depth-1 best-effort
reader that never takes does not reliably produce SAMPLE_LOST, so
events_seen stayed 0 and the final EXPECT_GT(events_seen, 0u) failed for
a reason unrelated to any deadlock.

Guard the registration with if(rmw_implementation MATCHES "fastrtps") so
it only runs for the fastrtps variants, and change the events_seen == 0
guard from EXPECT_GT to GTEST_SKIP so an un-exercised scenario is
reported as skipped rather than a misleading pass or a spurious failure.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: Thomas Moore <thomas.moore@torc.ai>

Author: thomasmoore-torc

test_rmw_implementation/CMakeLists.txt

@@ -309,15 +309,21 @@ if(BUILD_TESTING)
     )
 
     # Reproduces an AB-BA lock-order inversion between rmw_take_event(MESSAGE_LOST)
-    # and on_sample_lost. Requires real SAMPLE_LOST, so intra-process delivery is
-    # disabled via the profile below (Fast DDS only; ignored by other implementations).
-    ament_add_ros_isolated_gtest_test(test_event_message_lost_deadlock
-      TEST_NAME test_event_message_lost_deadlock${target_suffix}
-      TIMEOUT 60
-      ENV
-        ${rmw_implementation_env_var}
-        FASTRTPS_DEFAULT_PROFILES_FILE=${CMAKE_CURRENT_SOURCE_DIR}/test/no_intraprocess_profile.xml
-    )
+    # and on_sample_lost. This is specific to rmw_fastrtps: it relies on disabling
+    # intra-process delivery (via the Fast DDS profile below, a no-op for other
+    # implementations) to force real SAMPLE_LOST. Other implementations do not
+    # reliably produce SAMPLE_LOST for this pattern, so registering it for them only
+    # yields false failures; restrict registration to the fastrtps variants. (The test
+    # itself also skips cleanly if no loss is generated.)
+    if(rmw_implementation MATCHES "fastrtps")
+      ament_add_ros_isolated_gtest_test(test_event_message_lost_deadlock
+        TEST_NAME test_event_message_lost_deadlock${target_suffix}
+        TIMEOUT 60
+        ENV
+          ${rmw_implementation_env_var}
+          FASTRTPS_DEFAULT_PROFILES_FILE=${CMAKE_CURRENT_SOURCE_DIR}/test/no_intraprocess_profile.xml
+      )
+    endif()
   endfunction()
 
   call_for_each_rmw_implementation(test_api)

test_rmw_implementation/test/test_event_message_lost_deadlock.cpp

@@ -210,9 +210,14 @@ TEST_F(TestEventMessageLostDeadlock, take_event_does_not_deadlock_with_on_sample
   EXPECT_EQ(RMW_RET_OK, rmw_destroy_subscription(node, sub));
   EXPECT_EQ(RMW_RET_OK, rmw_destroy_publisher(node, pub));
 
-  // Guard against a misleading pass: if no loss was ever generated the R->E edge never
-  // ran. Most commonly this means intra-process delivery was left enabled.
-  EXPECT_GT(events_seen.load(), 0u)
-    << "No SAMPLE_LOST was generated, so the lock-order inversion was not exercised. "
-       "Ensure intra-process delivery is disabled (see the profile in the CMake env).";
+  // If no loss was ever generated, the R->E edge never ran, so the scenario was not
+  // exercised and "no deadlock" proves nothing. This happens when intra-process delivery
+  // was not disabled, or on an implementation that does not produce SAMPLE_LOST for a
+  // depth-1 best-effort reader that never takes. Skip cleanly rather than reporting a
+  // misleading pass or a failure unrelated to any deadlock.
+  if (events_seen.load() == 0u) {
+    GTEST_SKIP()
+      << "No SAMPLE_LOST was generated, so the lock-order inversion was not exercised. "
+         "Ensure intra-process delivery is disabled (see the profile in the CMake env).";
+  }
 }