return nextIndex >= 0;
    }

    /**
     * Checks whether nextIndex is valid; if so setting nextItem. Stops iterator when either hits
     * putIndex or sees null item.
     */
    private void checkNext() {
      if (nextIndex == putIndex) {
        nextIndex = -1;
        nextItem = null;
      } else {
        nextItem = items[nextIndex];
        if (nextItem == null) nextIndex = -1;
      }
    }

      return nextIndex >= 0;
    }

    /**
     * Checks whether nextIndex is valid; if so setting nextItem. Stops iterator when either hits
     * putIndex or sees null item.
     */
    private void checkNext() {
      if (nextIndex == putIndex) {
        nextIndex = -1;
        nextItem = null;
      } else {
        nextItem = items[nextIndex];
        if (nextItem == null) nextIndex = -1;
      }
    }

		}

		if err := DB.Create(&pet).Error; err != nil {
			t.Fatalf("errors happened when create: %v", err)
		}

		CheckPet(t, pet, pet)

		var pet2 Pet
		DB.Preload("Toy").Find(&pet2, "id = ?", pet.ID)
		CheckPet(t, pet2, pet)
	})

	t.Run("Slice", func(t *testing.T) {
		pets := []Pet{{
			Name: "PolymorphicHasOne-Slice-1",

		// user pet
		if users2[idx].NamedPet == nil {
			t.Fatalf("Failed to load NamedPet")
		}
		CheckPet(t, *user.NamedPet, *users2[idx].NamedPet)
		// manager pet
		if users2[idx].Manager.NamedPet == nil {
			t.Fatalf("Failed to load NamedPet")
		}
		CheckPet(t, *user.Manager.NamedPet, *users2[idx].Manager.NamedPet)
	}
}

func TestJoinsPreload_Issue7013(t *testing.T) {

		return errors.New("public key authority validation requested but no ca public key specified.")
	}

	cert, ok := clientKey.(*ssh.Certificate)
	if !ok {
		return errSftpPublicKeyWithoutCert
	}

	// ssh.CheckCert called by ssh.Authenticate accepts certificates
	// with empty principles list so we block those in here.
	if len(cert.ValidPrincipals) == 0 {
		return errSftpCertWithoutPrincipals
	}

	var pets []Pet
	DB.Model(&user).Where("name = ?", user.Pets[0].Name).Association("Pets").Find(&pets)

	if len(pets) != 1 {
		t.Fatalf("should only find one pets, but got %v", len(pets))
	}

	CheckPet(t, pets[0], *user.Pets[0])

	if count := DB.Model(&user).Where("name = ?", user.Pets[1].Name).Association("Pets").Count(); count != 1 {
		t.Fatalf("should only find one pets, but got %v", count)
	}

		})

		for _, pet := range users2[2].Pets[0:2] {
			if pet.Toy.Name != "" {
				t.Errorf("No toy should for user %v's pet %v but got %v", 3, pet.Name, pet.Toy.Name)
			}
		}

		CheckPet(t, *users2[2].Pets[2], *users[2].Pets[2])
	}
}

func TestPreloadEmptyData(t *testing.T) {
	user := *GetUser("user_without_associations", Config{})
	DB.Create(&user)

		// user pet
		if users2[idx].NamedPet == nil {
			t.Fatalf("Failed to load NamedPet")
		}
		CheckPet(t, *user.NamedPet, *users2[idx].NamedPet)
		// manager pet
		if users2[idx].Manager.NamedPet == nil {
			t.Fatalf("Failed to load NamedPet")
		}
		CheckPet(t, *user.Manager.NamedPet, *users2[idx].Manager.NamedPet)
	}
}

func TestGenericsPreloads(t *testing.T) {