Fix failing test (include duplicate check)

src/app/game-model/GameModel.ts

@@ -25,9 +25,12 @@ export class GameModel {
   }
 
   addGamesystem(gamesystem: Gamesystem<any, any>) {
+    if(this.findGamesystem(gamesystem.componentName) == undefined) {
       this._gamesystems.push(gamesystem);
     }
 
+  }
+
   removeGamesystem(gamesystem : Gamesystem<any, any>) {
     this._gamesystems = this._gamesystems.filter(g => g !== gamesystem);
   }