if err := DB.AutoMigrate(&LevelC1{}, &LevelC2{}, &LevelC3{}); err != nil {
		t.Error(err)
	}

	level2 := LevelC2{
		Value: "c2",
		LevelC1: LevelC1{
			Value: "c1",
		},
	}
	DB.Create(&level2)

	want := []LevelC3{
		{
			Value:   "c3-1",
			LevelC2: level2,
		}, {
			Value:   "c3-2",
			LevelC2: level2,
		},
	}