var companies []Company
	if DB.Model(&users).Association("Company").Find(&companies); len(companies) != 3 {
		t.Errorf("companies count should be %v, but got %v", 3, len(companies))
	}

	var managers []User
	if DB.Model(&users).Association("Manager").Find(&managers); len(managers) != 2 {
		t.Errorf("managers count should be %v, but got %v", 2, len(managers))
	}

	// Append
	DB.Model(&users).Association("Company").Append(