Cleanup usage of PHPUnit 4.8 aliased classes

+++ b/core/tests/bootstrap.php
@@ -180,19 +171,3 @@ function drupal_phpunit_populate_class_loader() {
-// PHPUnit 4 to PHPUnit 6 bridge. Tests written for PHPUnit 4 need to work on
-// PHPUnit 6 with a minimum of fuss.

This is a BC layer, so removing this could/would be disruptive to contrib.

At the very least we need a Change Record. But maybe the removing of the BC part needs to wait for D9, and we can only clean up core dependencies on the BC layer, probably depending on how disruptive we think this to be.

Ugh, old page submitted, files in #15 got hidden, but I can't show them, they are not in my files list?

+++ b/core/tests/bootstrap.php
@@ -180,19 +171,3 @@ function drupal_phpunit_populate_class_loader() {
-// PHPUnit 4 to PHPUnit 6 bridge. Tests written for PHPUnit 4 need to work on
-// PHPUnit 6 with a minimum of fuss.
-if (version_compare($phpunit_version, '6.1', '>=')) {
-  class_alias('\PHPUnit\Framework\AssertionFailedError', '\PHPUnit_Framework_AssertionFailedError');
-  class_alias('\PHPUnit\Framework\Constraint\Count', '\PHPUnit_Framework_Constraint_Count');
-  class_alias('\PHPUnit\Framework\Error\Error', '\PHPUnit_Framework_Error');
-  class_alias('\PHPUnit\Framework\Error\Warning', '\PHPUnit_Framework_Error_Warning');
-  class_alias('\PHPUnit\Framework\ExpectationFailedException', '\PHPUnit_Framework_ExpectationFailedException');
-  class_alias('\PHPUnit\Framework\Exception', '\PHPUnit_Framework_Exception');
-  class_alias('\PHPUnit\Framework\MockObject\Matcher\InvokedRecorder', '\PHPUnit_Framework_MockObject_Matcher_InvokedRecorder');
-  class_alias('\PHPUnit\Framework\SkippedTestError', '\PHPUnit_Framework_SkippedTestError');
-  class_alias('\PHPUnit\Framework\TestCase', '\PHPUnit_Framework_TestCase');
-  class_alias('\PHPUnit\Util\Test', '\PHPUnit_Util_Test');
-  class_alias('\PHPUnit\Util\Xml', '\PHPUnit_Util_XML');
-}

I think we can only remove this in Drupal 9. Maybe the best way here is to do this in a deprecated way - ie. add classes that are deprecated but extend the PHPunit class. That way we can do the removal cleanly.

Why can't we just break BC here? Every major release has broken tests for me(See DER HEAD test issue). It is not breaking any runtime code it will just break the tests which can be fixed after updating phpunit which you are supposed to do and then replacing some use statements. I think a proper CR would the job. Last interdiff feels like maintaining PHPUnit 4 in core.

The scope here is usage according to the IS. Let's remove usages of Old_Skool_PHPUnit_Test_Classes for this issue, and then remove the aliasing in a follow-up. That gives us a relatively easy review, and we can decide which supported version of PHPUnit we want to target in the near future before we decide on how BC works. #2950132: Support PHPUnit 7 optionally in Drupal 8, while keeping support for ^6.5 #3039275: phpunit-mock-objects is marked as "abandoned" when composer.lock is rebuilt

https://phpunit.de/supported-versions.html

Here's the follow-up: #3063182: Remove PHPUnit 4.8 class aliasing BC layer

Added follow-up issue based on #9: #3073318: Remove usages of \PHPUnit_Framework_MockObject_MockObject

I verified that a search for 'PHPUnit_' only yields MockObject references which will be handled above, or references within the aliasing code, which will be handled in #3063182: Remove PHPUnit 4.8 class aliasing BC layer

LGTM.

NICE! 👏

Committed 50a6a9e and pushed to 8.8.x. Thanks!

I think #3063182: Remove PHPUnit 4.8 class aliasing BC layer and #3073318: Remove usages of \PHPUnit_Framework_MockObject_MockObject are next?