16 files declare their use of Action

ActionFormAjaxTest.php in core/modules/action/tests/src/FunctionalJavascript/ActionFormAjaxTest.php
ActionResourceTestBase.php in core/modules/system/tests/src/Functional/Rest/ActionResourceTestBase.php
ActionTest.php in core/modules/jsonapi/tests/src/Functional/ActionTest.php
ActionTest.php in core/modules/system/tests/src/Kernel/Action/ActionTest.php
CommentActionsTest.php in core/modules/comment/tests/src/Kernel/CommentActionsTest.php
ConfigEntityImportTest.php in core/modules/system/tests/src/Kernel/Entity/ConfigEntityImportTest.php
ConfigInstallProfileOverrideTest.php in core/modules/config/tests/src/Functional/ConfigInstallProfileOverrideTest.php
ConfigurationTest.php in core/modules/action/tests/src/Functional/ConfigurationTest.php
DeleteActionTest.php in core/tests/Drupal/KernelTests/Core/Action/DeleteActionTest.php
MigrateActionsTest.php in core/modules/system/tests/src/Kernel/Migrate/d6/MigrateActionsTest.php
MigrateActionsTest.php in core/modules/system/tests/src/Kernel/Migrate/d7/MigrateActionsTest.php
NodeActionsConfigurationTest.php in core/modules/node/tests/src/Functional/NodeActionsConfigurationTest.php
PublishActionTest.php in core/tests/Drupal/KernelTests/Core/Action/PublishActionTest.php
SaveActionTest.php in core/tests/Drupal/KernelTests/Core/Action/SaveActionTest.php
UnpublishByKeywordActionTest.php in core/modules/node/tests/src/Kernel/Action/UnpublishByKeywordActionTest.php
user.module in core/modules/user/user.module
Enables the user registration and login system.

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