if err := DB.AutoMigrate(new(Level1), new(Level2)); err != nil {
		t.Error(err)
	}

	lvl := Level1{
		Name: "l1",
		Level2s: []Level2{
			{Name: "l2-1"}, {Name: "l2-2"},
		},
	}
	DB.Save(&lvl)

	var called int64
	DB.Callback().Query().After("gorm:query").Register("TestPreloadManyToManyCallbacks", func(_ *gorm.DB) {
		atomic.AddInt64(&called, 1)
	})