Custom assertion examples are missing

[Artem]

Hello, I was trying to make a custom assertion and looked through the documentation:
https://assertj.github.io/doc/#assertj-core-custom-assertions

It seems like this paragraph is missing.

There is an article here https://joel-costigliola.github.io/assertj/assertj-core-custom-assertions.html but it also seems to be a bit outdated.

While there is an example of extending an AbstractAssert, it'd be nice to have an example of a AbstractIterableAssert too.

I believe I can adopt an example from an old site but don't have enough knowledge to write about AbstractIterableAssert as some things are unclear.

[Stefano Cordio]

That's right, that paragraph has not been rewritten yet. However, https://joel-costigliola.github.io/assertj/assertj-core-custom-assertions.html should be a good starting point.

Is there anything specific you need help with?

[Artem]

@scordio , I had a lot of checks that required using method .usingElementComparatorIgnoringFields(...)

I thought it's a good reason to make a custom assertion. I've looked through an old article and
extended AbstractAssert but then understood that it's required to extend AbstractIterableAssert.
IDEA helped to override newAbstractIterableAssert and toAssert. These are the methods that maybe lack some documentation because it's not clear do they have to have additional logic.

My final assertion looks like this:

private static class StarredFolderListAssert extends AbstractIterableAssert<StarredFolderListAssert, List<StarredEntity>, StarredEntity, StarredFolderAssert> {

        List<StarredEntity> entities = new ArrayList<>();

        public StarredFolderListAssert(List<StarredEntity> starredEntities, Class<?> selfType) {
            super(starredEntities, selfType);
            entities.addAll(starredEntities);
        }

        @Override
        protected StarredFolderListAssert newAbstractIterableAssert(Iterable iterable) {
            return null;
        }

        public static StarredFolderListAssert assertThat(List<StarredEntity> actual) {
            return new StarredFolderListAssert(actual, StarredFolderListAssert.class);
        }

        public StarredFolderListAssert containsStarredBaseInfo(StarredEntity entity) {
            Assertions.assertThat(entities).usingElementComparatorIgnoringFields("setting", "starredAt", "parent").contains(entity);
            return this;
        }

        @Override
        protected StarredFolderAssert toAssert(StarredEntity value, String description) {
            return null;
        }
    }

    private static class StarredFolderAssert extends AbstractAssert<StarredFolderAssert, StarredEntity> {

        public StarredFolderAssert(StarredEntity entity, Class<?> selfType) {
            super(entity, selfType);
        }
    }

[Artem]

Maybe @joel-costigliola has something to add :)

[Joel Costigliola]

In addition to the documentation, it would be great to have StarredEntity and StarredFolder code so that we can add you example example in assertj-examples.

[Artem]

@scordio , @joel-costigliola , that was a long delay from me, but here it is:

@Data
@AllArgsConstructor
@Builder
 public static class StarredEntity {
        Integer id;
        String title;
        Boolean isProject;
        Long starredAt;
        Settings setting;
        Long order;
    }

I wanted to ignore several fields that's why a custom assertion was written. However, it was not clear what does newAbstractIterableAssert and toAssert methods do?

[Joel Costigliola]

I have migrated the documentation of the old site to the new one. see https://assertj.github.io/doc/#assertj-core-custom-assertions.

[Joel Costigliola]

@KroArtem is used by navigation method like first() that returns assertions for the first element of the iterable.
In your case simply build a StarredFolderAssert.

newAbstractIterableAssert is used to build the assert instance with a filtered iterable (basically after filteredOn is called), simply create another instance of your own iterable assert with the given iterable.
Ex:

@Override
protected StarredFolderListAssert newAbstractIterableAssert(Iterable iterable) {
  return new StarredFolderListAssert(new ArrayList<>(iterable), StarredFolderListAssert.class);
}

We will add javadoc for both newAbstractIterableAssert and toAssert.

Note that you could inherit from AbstractListAssert since it looks like you want to assert on List<StarredEntity>

[Artem]

Thanks! I think this ticket can be closed now.