if result.RowsAffected != int64(len(users)) {
		t.Errorf("affected rows should be %v, but got %v", len(users), result.RowsAffected)
	}

	for _, user := range users {
		if user.ID == 0 {
			t.Fatalf("failed to fill user's ID, got %v", user.ID)
		} else {
			var newUser User
			if err := DB.Where("id = ?", user.ID).Preload(clause.Associations).First(&newUser).Error; err != nil {
				t.Fatalf("errors happened when query: %v", err)