cu_cp: add unit test for amf connection loss without connected dus

Author: FabianEckermann

lib/cu_cp/cu_cp_controller/amf_connection_manager.cpp

@@ -59,7 +59,6 @@ void amf_connection_manager::connect_to_amf(std::promise<bool>* completion_signa
 async_task<void> amf_connection_manager::disconnect_amf()
 {
   if (ngaps.get_ngaps().empty() or amfs_connected.empty()) {
-    logger.error("No NGAP interface available to disconnect from AMF");
     return launch_async([](coro_context<async_task<void>>& ctx) {
       CORO_BEGIN(ctx);
       CORO_RETURN();

tests/unittests/cu_cp/cu_cp_connectivity_test.cpp

@@ -80,6 +80,18 @@ TEST_F(cu_cp_connectivity_test, when_ng_setup_fails_then_cu_cp_is_not_in_amf_con
   ASSERT_FALSE(get_cu_cp().get_ng_handler().amfs_are_connected());
 }
 
+TEST_F(cu_cp_connectivity_test, when_amf_connection_is_lost_and_no_dus_are_connected_then_no_amfs_are_connected)
+{
+  // Run NG setup to completion.
+  run_ng_setup();
+
+  // Drop AMF connection.
+  ASSERT_TRUE(drop_amf_connection(0));
+
+  // Check that CU-CP is still running but not connected to AMF.
+  ASSERT_FALSE(this->get_cu_cp().get_ng_handler().amfs_are_connected());
+}
+
 TEST_F(cu_cp_connectivity_test, when_amf_connection_is_lost_then_connected_ues_are_released_and_new_ues_are_rejected)
 {
   // Run NG setup to completion.

tests/unittests/cu_cp/cu_cp_test_environment.cpp

@@ -333,6 +333,8 @@ bool cu_cp_test_environment::drop_amf_connection(unsigned amf_idx)
     return false;
   }
   it->second.amf_stub->drop_connection();
+  // Wait for the CU-CP to process the disconnection.
+  cu_cp_workers->wait_pending_tasks();
   return true;
 }