diff --git a/src/Plugin/PluginManager.py b/src/Plugin/PluginManager.py
index 4854b218..36cc3486 100644
--- a/src/Plugin/PluginManager.py
+++ b/src/Plugin/PluginManager.py
@@ -40,11 +40,12 @@ class PluginManager:
 
     # Load all plugin
     def loadPlugins(self):
+        all_loaded = True
         s = time.time()
         for dir_name in sorted(os.listdir(self.plugin_path)):
             dir_path = os.path.join(self.plugin_path, dir_name)
             if dir_name == "__pycache__":
-                continue # skip
+                continue  # skip
             if dir_name.startswith("disabled"):
                 continue  # Dont load if disabled
             if not os.path.isdir(dir_path):
@@ -56,12 +57,14 @@ class PluginManager:
                 __import__(dir_name)
             except Exception as err:
                 self.log.error("Plugin %s load error: %s" % (dir_name, Debug.formatException(err)))
+                all_loaded = False
             if dir_name not in self.plugin_names:
                 self.plugin_names.append(dir_name)
 
         self.log.debug("Plugins loaded in %.3fs" % (time.time() - s))
         for func in self.after_load:
             func()
+        return all_loaded
 
     # Reload all plugins
     def reloadPlugins(self):
@@ -153,6 +156,13 @@ def acceptPlugins(base_class):
 
 # Register plugin to class name decorator
 def registerTo(class_name):
+    if config.debug:
+        import gc
+        for obj in gc.get_objects():
+            if type(obj).__name__ == class_name:
+                raise Exception("Class %s instances already present in memory" % class_name)
+                break
+
     plugin_manager.log.debug("New plugin registered to: %s" % class_name)
     if class_name not in plugin_manager.plugins:
         plugin_manager.plugins[class_name] = []
diff --git a/src/Test/conftest.py b/src/Test/conftest.py
index 9a664451..1db8bd69 100644
--- a/src/Test/conftest.py
+++ b/src/Test/conftest.py
@@ -78,7 +78,9 @@ config.data_dir = TEST_DATA_PATH  # Use test data for unittests
 
 os.chdir(os.path.abspath(os.path.dirname(__file__) + "/../.."))  # Set working dir
 
-PluginManager.plugin_manager.loadPlugins()
+all_loaded = PluginManager.plugin_manager.loadPlugins()
+assert all_loaded, "There was error loading plugins"
+
 config.loadPlugins()
 config.parse()  # Parse again to add plugin configuration options