Two steps allow tests to run with phpunit 8.5 and php 8.1:

• Replace PHPUnit_Framework_TestCase with \PHPUnit\Framework\TestCase in all test files
• Add return type declaration : void to setUp() and tearDown() in all test classes

For the first step, source-level compatibility for newer and older phpunit can be achieved by

+if (!class_exists('PHPUnit_Framework_TestCase')) {
+    class_alias('\PHPUnit\Framework\TestCase', 'PHPUnit_Framework_TestCase');
+}

However, for the second step, source-level compatibility seems impossible for both newer and older PHP. PHP >= 8.0 requires compatible return types [1], while PHP < 7.0 does not recognize return types [2]. I'm afraid idiorm needs to use a magic like sed -i 's#: void##' test/*.php before running tests for older PHP versions.

[1] https://php.watch/versions/8.0/lsp-errors
[2] https://www.php.net/manual/en/migration70.new-features.php

Nice - thanks for your help - I think we have a PR we can merge now.

Glad to help :)