I noticed the following while running the tests:
PHPUnit\Event\TestRunner\WarningTriggered: Class Drupal\commerce_checkout_test\Plugin\Commerce\CheckoutPane\CheckoutTest declared in /builds/project/commerce/modules/checkout/tests/modules/commerce_checkout_test/src/Plugin/Commerce/CheckoutPane/CheckoutTest.php does not extend PHPUnit\Framework\TestCase
But CheckoutTest is a test checkouut pane, not a test. Let's rename it to avoid the confusion... The class shouldn't end with Test.
Active
3.0
Tests
[#3541094] fix: The CheckoutTest pane is confusing the tests