t.Error("RowsAffected should be correct when do batch update")
	}

	animal = Animal{From: "somewhere"}              // No name fields, should be filled with the default value (galeone)
	DB.Save(&animal).Update("From", "a nice place") // The name field shoul be untouched
	DB.First(&animal, animal.Counter)
	if animal.Name != "galeone" {
		t.Errorf("Name fields shouldn't be changed if untouched, but got %v", animal.Name)
	}

In this case, you could want to document how that external API *should* look like. What *path operation* it should have, what body it should expect, what response it should return, etc.

## An app with callbacks

Let's see all this with an example.

Imagine you develop an app that allows creating invoices.

These invoices will have an `id`, `title` (optional), `customer`, and `total`.

    assertEquals("Cause should be available.", exception, handler.exception);
    assertEquals("EventBus should be available.", eventBus, handler.context.getEventBus());
    assertEquals("Event should be available.", EVENT, handler.context.getEvent());
    assertEquals("Subscriber should be available.", subscriber, handler.context.getSubscriber());
    assertEquals(
        "Method should be available.",

    assertEquals("Cause should be available.", exception, handler.exception);
    assertEquals("EventBus should be available.", eventBus, handler.context.getEventBus());
    assertEquals("Event should be available.", EVENT, handler.context.getEvent());
    assertEquals("Subscriber should be available.", subscriber, handler.context.getSubscriber());
    assertEquals(
        "Method should be available.",

	}

	err = DB.Model([1]*Product5{&p}).Update("name", "update_name_3").Error
	if err != nil {
		t.Fatalf("should update success, but got err %v", err)
	}
	if beforeUpdateCall != 2 {
		t.Fatalf("before update should be called")
	}

	err = DB.Model([1]Product5{p}).Update("name", "update_name_4").Error
	if !errors.Is(err, gorm.ErrInvalidValue) {

	}

	if err := DB.Find(&langs, "code = ?", lang.Code).Error; err != nil {
		t.Errorf("no error should happen when find languages with code, but got %v", err)
	} else if len(langs) != 1 {
		t.Errorf("should only find only 1 languages, but got %+v", langs)
	} else if langs[0].Name != "upsert-new" {
		t.Errorf("should update name on conflict, but got name %+v", langs[0].Name)
	}

    assertEquals("Should be able to peek() at first element", "A", peekingIterator.peek());
    assertEquals(
        "Should be able to peek() first element multiple times", "A", peekingIterator.peek());
    assertEquals(
        "next() should still return first element after peeking", "A", peekingIterator.next());

    assertEquals("Should be able to peek() at middle element", "B", peekingIterator.peek());

    assertSame(
        "toArray(sameSizeE[]) should return the given array", array, collection.toArray(array));
    expectArrayContentsAnyOrder(createSamplesArray(), array);
  }

  @CollectionFeature.Require(KNOWN_ORDER)
  public void testToArray_rightSizedArray_ordered() {
    E[] array = getSubjectGenerator().createArray(getNumElements());
    assertSame(

    assertSame(
        "toArray(sameSizeE[]) should return the given array", array, collection.toArray(array));
    expectArrayContentsAnyOrder(createSamplesArray(), array);
  }

  @CollectionFeature.Require(KNOWN_ORDER)
  public void testToArray_rightSizedArray_ordered() {
    E[] array = getSubjectGenerator().createArray(getNumElements());
    assertSame(

		t.Fatalf("Should find 1 tags after Delete")
	}

	if DB.Model(&blog).Association("Tags").Count() != 1 {
		t.Fatalf("Blog should has three tags after Delete")
	}

	DB.Model(&blog).Association("Tags").Delete(tag3)
	var tags4 []Tag
	DB.Model(&blog).Association("Tags").Find(&tags4)
	if !compareTags(tags4, []string{"tag6"}) {
		t.Fatalf("Tag should not be deleted when Delete with a unrelated tag")