public static ProfileManager getInstance() {
        if (INSTANCE == null) {
            INSTANCE = new ProfileManager();
        }
        return INSTANCE;
    }
@Test
    public void testSingleton() {
        ProfileManager instance1 = ProfileManager.getInstance();
        ProfileManager instance2 = ProfileManager.getInstance();
        assertSame(instance1, instance2, "ProfileManager should be singleton");
    }