assertEquals( 0, otnPerson.getOtnIdCounter() );
assertEquals( 0, otnCheese.getOtnIdCounter() );
assertEquals( 0, otnCat.getOtnIdCounter() );
wm.insert( new Person() );
wm.insert( new Cat("yyy") );
wm.insert( new Cheese() );
assertEquals( 2, otnPerson.getOtnIdCounter() );
assertEquals( 4, otnCheese.getOtnIdCounter() );
assertEquals( 2, otnCat.getOtnIdCounter() );