While running MediaWiki core tests with Wikibase, I eventually got a failure:
```
1) PrefixUniquenessTest::testPrefixes
Module prefix 'wbeu' is shared between Wikibase\Client\Api\ApiListEntityUsage and Wikibase\Client\Api\ApiPropsEntityUsage
tests/phpunit/includes/api/PrefixUniquenessTest.php:24
tests/phpunit/MediaWikiTestCase.php:469
maintenance/doMaintenance.php:94
```
`PrefixUniquenessTest::testPrefixes` is described as:
> Checks that all API query modules, core and extensions, have unique prefixes.
It is part of mediawiki/core, since the test is not a structure test, it is never run for extension, only for mediawiki/core patches. Which explains why it has never been noticed yet.
Related code:
```
client/includes/Api/ApiListEntityUsage.php:34: parent::__construct( $query, $moduleName, 'wbeu' );
client/includes/Api/ApiPropsEntityUsage.php:32: parent::__construct( $query, $moduleName, 'wbeu' );
```
Module references:
| Class: | ApiPropsEntityUsage | ApiListEntityUsage
|--|--|--
| Doc | https://www.mediawiki.org/wiki/Wikibase/API#wbentityusage | https://www.mediawiki.org/wiki/Wikibase/API#wblistentityusage
| Call | list=wbentityusagelist | prop=wbentityusage
| Initial commit | 382ac75c7b8cecf7ab518e5119e5cd2f1187dbc3 | c2364b8ac2ec62b74dc076129f12f0a3515b94e3
| Feature task | T143147 | T143118