Running PHPUnit fails
$ ./vendor/bin/phpunit
PHP Fatal error: Trait "Drupal\Tests\config_filter\Kernel\ConfigStorageTestTrait" not found in /var/www/html/web/modules/contrib/config_split/tests/src/Kernel/InactiveSplitTest.php on line 14
Create a site with config_split enabled
Do not also require config_filter
Run PHPUnit
Amend config_split/tests/src/Kernel/InactiveSplitTest.php
Remove or replace the reference to:
use Drupal\Tests\config_filter\Kernel\ConfigStorageTestTrait;
&
use ConfigStorageTestTrait;
2nd solution
add the requirement for drupal/config_flter back into the composer.json and config_split.info.yml files.
Choose an approach
Implement the Solution
Test
Closed: works as designed
2.0
Documentation
Check composer.json
Config Filter is required when running tests.
If you want to run php unit tests of config split in a different environment than the default it is your responsibility to require also config filter.