Added a test to check if a custom subscriber was created correctly.

rclcpp/test/rclcpp/CMakeLists.txt

@@ -100,6 +100,13 @@ if(TARGET test_create_subscription)
     "test_msgs"
   )
 endif()
+ament_add_gtest(test_create_custom_subscription test_create_custom_subscription.cpp)
+if(TARGET test_create_custom_subscription)
+  target_link_libraries(test_create_custom_subscription ${PROJECT_NAME})
+  ament_target_dependencies(test_create_custom_subscription
+    "test_msgs"
+  )
+endif()
 function(test_add_callback_groups_to_executor_for_rmw_implementation)
   set(rmw_implementation_env_var RMW_IMPLEMENTATION=${rmw_implementation})
   ament_add_gmock(test_add_callback_groups_to_executor${target_suffix} test_add_callback_groups_to_executor.cpp

rclcpp/test/rclcpp/test_create_custom_subscription.cpp

@@ -0,0 +1,73 @@
+#include <gtest/gtest.h>
+
+#include <chrono>
+#include <memory>
+#include <type_traits>
+
+#include "rclcpp/subscription.hpp"
+#include "rclcpp/create_subscription.hpp"
+#include "rclcpp/node.hpp"
+#include "test_msgs/msg/empty.hpp"
+#include "test_msgs/msg/empty.h"
+
+using namespace std::chrono_literals;
+
+class TestCreateSubscription : public ::testing::Test
+{
+public:
+  void SetUp() override
+  {
+    rclcpp::init(0, nullptr);
+  }
+
+  void TearDown() override
+  {
+    rclcpp::shutdown();
+  }
+};
+
+template<
+  typename MessageT,
+  typename AllocatorT = std::allocator<void>,
+  typename SubscribedT = typename rclcpp::TypeAdapter<MessageT>::custom_type,
+  typename ROSMessageT = typename rclcpp::TypeAdapter<MessageT>::ros_message_type,
+  typename MessageMemoryStrategyT = rclcpp::message_memory_strategy::MessageMemoryStrategy<
+    ROSMessageT,
+    AllocatorT
+  >>
+class CustomSubscription : public rclcpp::Subscription<
+  MessageT, AllocatorT, SubscribedT, ROSMessageT, MessageMemoryStrategyT> 
+{
+public:
+
+  template <typename... Args>
+  CustomSubscription(Args &&...args) : rclcpp::Subscription<
+    MessageT, AllocatorT, SubscribedT, ROSMessageT, MessageMemoryStrategyT>(
+    std::forward<Args>(args)...) {}
+};
+
+TEST_F(TestCreateSubscription, create) {
+  using MessageT = test_msgs::msg::Empty;
+
+  auto node = std::make_shared<rclcpp::Node>("my_node", "/ns");
+  const rclcpp::QoS qos(10);
+  auto options = rclcpp::SubscriptionOptions();
+  auto callback = [](MessageT::ConstSharedPtr) {};
+
+  using CallbackT = std::decay_t<decltype(callback)>;
+  using AllocatorT = std::allocator<void>;
+  using SubscriptionT = CustomSubscription<MessageT, AllocatorT>;
+  using CallbackMessageT =
+      typename rclcpp::subscription_traits::has_message_type<CallbackT>::type;
+  using MessageMemoryStrategyT =
+      rclcpp::message_memory_strategy::MessageMemoryStrategy<CallbackMessageT,
+                                                             AllocatorT>;
+
+  auto subscription = rclcpp::create_subscription<
+    MessageT, CallbackT, AllocatorT, SubscriptionT, MessageMemoryStrategyT>(
+    node, "topic_name", qos, std::move(callback), options);
+
+  ASSERT_NE(nullptr, subscription);
+  EXPECT_STREQ("/ns/topic_name", subscription->get_topic_name());
+  static_assert(std::is_same_v<std::decay_t<decltype(*subscription.get())>, SubscriptionT>);
+}