8 files declare their use of KernelPluginManagerTestBase in Purge 8.3

PluginManagerTest.php in tests/src/Kernel/Purger/PluginManagerTest.php

PluginManagerTest.php in tests/src/Kernel/Processor/PluginManagerTest.php

PluginManagerTest.php in tests/src/Kernel/Queue/PluginManagerTest.php

PluginManagerTest.php in tests/src/Kernel/Invalidation/PluginManagerTest.php

PluginManagerTest.php in tests/src/Kernel/TagsHeader/PluginManagerTest.php

PluginManagerTest.php in tests/src/Kernel/Queuer/PluginManagerTest.php

PluginManagerTest.php in tests/src/Kernel/DiagnosticCheck/PluginManagerTest.php

PluginTestBase.php in tests/src/Kernel/Queue/PluginTestBase.php