I have opened a PR that should make testing possible again. Unfortunately, the Idiorm test suite does not appear to be passing on PHPUnit 8.5 and therefore doesn't pass on PHP 8.0 and above. So the unit tests would need to be updated for this branch to be merged. The would need to pass on PHP 5.2, 5.4, 5.6, 7.0, 7.1, 7.2, 7.3, 7.4, 8.0, 8.2

5.2 runs on PHPUnit 3.6
5.4 -> 7.4 runs on PHPUnit 4.8
8.0 and above runs on PHPUnit 8.5

PHPUnit 4.8 won't run on PHP8 because it uses the each function which no long exists.
Idiorms tests won't run on PHPUnit 8.5 because

PHP Fatal error:  Uncaught Error: Class "PHPUnit_Framework_TestCase" not found in /home/runner/work/idiorm/idiorm/test/CacheIntegrationTest.php:3