I'm developing a Wordpress plugin and wanted to use a test-driven approach so I installed PHPUnit and the WP CLI tool. I did wp scaffold plugin-tests my-plugin and it generated the scaffolding files just fine. I did bin/install-wp-tests.sh site_name user pass host and it did its thing with no errors. So I ran my tests and got:

❯ phpunit
Installing...
Running as single site... To run multisite, use -c tests/phpunit/multisite.xml
PHP Warning:  Class "PHPUnit\Framework\Error\Deprecated" not found in /private/var/folders/px/v5s4zb6n5bzbhpxvyvgt99x40000gn/T/wordpress-tests-lib/includes/phpunit6/compat.php on line 8

Warning: Class "PHPUnit\Framework\Error\Deprecated" not found in /private/var/folders/px/v5s4zb6n5bzbhpxvyvgt99x40000gn/T/wordpress-tests-lib/includes/phpunit6/compat.php on line 8
PHP Warning:  Class "PHPUnit\Framework\Error\Notice" not found in /private/var/folders/px/v5s4zb6n5bzbhpxvyvgt99x40000gn/T/wordpress-tests-lib/includes/phpunit6/compat.php on line 9

Warning: Class "PHPUnit\Framework\Error\Notice" not found in /private/var/folders/px/v5s4zb6n5bzbhpxvyvgt99x40000gn/T/wordpress-tests-lib/includes/phpunit6/compat.php on line 9
PHP Warning:  Class "PHPUnit\Framework\Error\Warning" not found in /private/var/folders/px/v5s4zb6n5bzbhpxvyvgt99x40000gn/T/wordpress-tests-lib/includes/phpunit6/compat.php on line 10

Warning: Class "PHPUnit\Framework\Error\Warning" not found in /private/var/folders/px/v5s4zb6n5bzbhpxvyvgt99x40000gn/T/wordpress-tests-lib/includes/phpunit6/compat.php on line 10
PHP Warning:  Class "PHPUnit\Framework\Warning" not found in /private/var/folders/px/v5s4zb6n5bzbhpxvyvgt99x40000gn/T/wordpress-tests-lib/includes/phpunit6/compat.php on line 12

Warning: Class "PHPUnit\Framework\Warning" not found in /private/var/folders/px/v5s4zb6n5bzbhpxvyvgt99x40000gn/T/wordpress-tests-lib/includes/phpunit6/compat.php on line 12
PHP Warning:  Class "PHPUnit\Framework\TestListener" not found in /private/var/folders/px/v5s4zb6n5bzbhpxvyvgt99x40000gn/T/wordpress-tests-lib/includes/phpunit6/compat.php on line 15

Warning: Class "PHPUnit\Framework\TestListener" not found in /private/var/folders/px/v5s4zb6n5bzbhpxvyvgt99x40000gn/T/wordpress-tests-lib/includes/phpunit6/compat.php on line 15
Not running ajax tests. To execute these, use --group ajax.
Not running ms-files tests. To execute these, use --group ms-files.
Not running external-http tests. To execute these, use --group external-http.
PHPUnit 12.0.10 by Sebastian Bergmann and contributors.

Runtime:       PHP 8.3.12
Configuration: /Volumes/Speicher/Jobs/sandboxes/wordpress/wp-content/plugins/quicksilver/phpunit.xml.dist

Looking at the repo for PHPUnit I find that there hasn't been a Framework/Error class since version 9.5, which is not compatible with PHP8+.

Any idea how to solve this?