if err := DB.AutoMigrate(&Level3{}, &Level2{}, &Level1{}); err != nil {
		t.Error(err)
	}

	want := Level1{
		Value: "Bob",
		Level2: &Level2{
			Value: "en",
			Level3: &Level3{
				Value: "native",
			},
		},
	}
	if err := DB.Save(&want).Error; err != nil {
		t.Error(err)
	}

	want2 := Level1{
		Value:  "Tom",
		Level2: nil,
	}