Change record status: 
Project: 
Introduced in branch: 
8.5.x
Introduced in version: 
8.5.0
Description: 

PHPUnit_Framework_BaseTestListener and similar classes are deprecated in PHPUnit 5 in favour of the fully namespaced PHPUnit\Framework\BaseTestListener and similar.

To smooth over the transition to PHPUnit 6 and later, specific traits have been added to the \Drupal\Tests\Listeners namespace to provide a forward and backward compatibility layer, and a single \Drupal\Tests\Listeners\DrupalListener added, replacing previous distinct listeners. The single listener then hands over execution to trait code that works across PHPUnit 4 to later versions.

This only affects developers that are adding custom PHPUnit listeners to their testing suites.

Impacts: 
Module developers