It appears that tests in the library `WikibaseDataModelSerialization` have been failing for some time now due to out of date dependencies (see original report below). These errors should be fixed, and indications of failing builds should be up to date.
**Acceptance Criteria**
- [ ] Tests pass in `WikibaseDataModelSerialization`
- [ ] Ensure that badges on readme.md are up to date or remove them to prevent misleading potential contributers
**Original Report:**
I wanted to work on a PR to address T323618 so I tried:
```
git clone https://github.com/wmde/WikibaseDataModelSerialization
composer install
composer test
```
Only to discover that the tests fail with a bunch of `Error: Class 'Wikibase\DataModel\Entity\NumericPropertyId' not found` errors.
I did some digging and this is apparently because #Wikibase-DataModel-Serialization depends on #wikibase-datamodel, where the `NumericPropertyId` class has been introduced in T289125. However #wikibase-datamodel has not had a release since and #Wikibase-DataModel-Serialization has been changed to use the new class in [a14086394e8cd813a29ddcae6c9338dc9665a1f3](https://github.com/wmde/WikibaseDataModelSerialization/commit/a14086394e8cd813a29ddcae6c9338dc9665a1f3) without updating the `wikibase/data-model` dependency in `composer.json`.
So I think a new version of #wikibase-datamodel should be released and the `composer.json` of #Wikibase-DataModel-Serialization should be updated accordingly. I was initially really confused why the README proudly declared "build passing" but [apparently the Travis CI is dead](https://travis-ci.org/github/wmde/WikibaseDataModelSerialization), having last run 2 years ago.