diff --git a/test_suite/FGTestApi/testGlobals.cxx b/test_suite/FGTestApi/testGlobals.cxx
index 5ee07e763..44a8c26ab 100644
--- a/test_suite/FGTestApi/testGlobals.cxx
+++ b/test_suite/FGTestApi/testGlobals.cxx
@@ -16,6 +16,7 @@
 #include <Main/options.hxx>
 #include <Main/util.hxx>
 #include <Main/FGInterpolator.hxx>
+#include <Main/locale.hxx>
 
 #include <Time/TimeManager.hxx>
 
@@ -78,6 +79,9 @@ void initTestGlobals(const std::string& testName)
      * destroyed via the subsystem manager.
      */
     globals->add_subsystem("events", globals->get_event_mgr(), SGSubsystemMgr::DISPLAY);
+    
+    // necessary to avoid asserts: mark FGLocale as initialized
+    globals->get_locale()->selectLanguage({});
 }
     
 bool logPositionToKML(const std::string& testName)
diff --git a/test_suite/unit_tests/AI/test_AIFlightPlan.cxx b/test_suite/unit_tests/AI/test_AIFlightPlan.cxx
index 833e83a20..2995a906c 100644
--- a/test_suite/unit_tests/AI/test_AIFlightPlan.cxx
+++ b/test_suite/unit_tests/AI/test_AIFlightPlan.cxx
@@ -49,7 +49,7 @@ void AIFlightPlanTests::setUp()
     FGTestApi::setUp::initTestGlobals("AI");
     FGTestApi::setUp::initNavDataCache();
 
-    globals->add_new_subsystem<FGAIManager>();
+    globals->add_new_subsystem<FGAIManager>(SGSubsystemMgr::GENERAL);
 
     auto props = globals->get_props();
     props->setBoolValue("sim/ai/enabled", true);
@@ -276,7 +276,7 @@ void AIFlightPlanTests::testAIFlightPlanLeftCircle()
         course += 10;
         const auto g1 = SGGeodesy::direct(lastWp->getPos(), course, SG_NM_TO_METER * 5.0);
         wp->setPos(g1);
-        wp->setName("testWp_" + i);
+        wp->setName("testWp_" + std::to_string(i));
         wp->setOn_ground(true);
         wp->setGear_down(true);
         wp->setSpeed(10);
diff --git a/test_suite/unit_tests/AI/test_TrafficMgr.cxx b/test_suite/unit_tests/AI/test_TrafficMgr.cxx
index bed1279f2..36ff0b8aa 100644
--- a/test_suite/unit_tests/AI/test_TrafficMgr.cxx
+++ b/test_suite/unit_tests/AI/test_TrafficMgr.cxx
@@ -56,7 +56,7 @@ void TrafficMgrTests::tearDown()
 }
 
 void TrafficMgrTests::testParse() {
-    globals->add_new_subsystem<FGTrafficManager>();
+    globals->add_new_subsystem<FGTrafficManager>(SGSubsystemMgr::GENERAL);
 
     globals->get_subsystem_mgr()->bind();
     globals->get_subsystem_mgr()->init();
@@ -108,7 +108,7 @@ void TrafficMgrTests::testTrafficManager()
 
     FGTestApi::setPositionAndStabilise(egeo->geod());
 
-    auto tmgr = globals->add_new_subsystem<FGTrafficManager>();
+    auto tmgr = globals->add_new_subsystem<FGTrafficManager>(SGSubsystemMgr::GENERAL);
 
     tmgr->bind();
     tmgr->init();
@@ -150,4 +150,4 @@ void TrafficMgrTests::testTrafficManager()
         counter++;
     }
    CPPUNIT_ASSERT_EQUAL(25, counter);
-}
\ No newline at end of file
+}
diff --git a/test_suite/unit_tests/AI/test_groundnet.cxx b/test_suite/unit_tests/AI/test_groundnet.cxx
index dbbbf9038..d5ae731cc 100644
--- a/test_suite/unit_tests/AI/test_groundnet.cxx
+++ b/test_suite/unit_tests/AI/test_groundnet.cxx
@@ -68,10 +68,10 @@ void GroundnetTests::setUp()
     ybbn->testSuiteInjectGroundnetXML(SGPath::fromUtf8(FG_TEST_SUITE_DATA) / "YBBN.groundnet.xml");
 
 
-    globals->add_new_subsystem<PerformanceDB>();
-    globals->add_new_subsystem<FGATCManager>();
-    globals->add_new_subsystem<FGAIManager>();
-    globals->add_new_subsystem<flightgear::AirportDynamicsManager>();
+    globals->add_new_subsystem<PerformanceDB>(SGSubsystemMgr::GENERAL);
+    globals->add_new_subsystem<FGATCManager>(SGSubsystemMgr::GENERAL);
+    globals->add_new_subsystem<FGAIManager>(SGSubsystemMgr::GENERAL);
+    globals->add_new_subsystem<flightgear::AirportDynamicsManager>(SGSubsystemMgr::GENERAL);
 
     globals->get_subsystem_mgr()->bind();
     globals->get_subsystem_mgr()->init();