6 files declare their use of AccessResultNeutral in Drupal 9

AccessResultNeutralTest.php in core/tests/Drupal/Tests/Core/Access/AccessResultNeutralTest.php

AccessResultTest.php in core/tests/Drupal/Tests/Core/Access/AccessResultTest.php

Contains \Drupal\Tests\Core\Access\AccessResultTest.

BlockPluginHasSettingsTrayFormAccessCheckTest.php in core/modules/settings_tray/tests/src/Unit/Access/BlockPluginHasSettingsTrayFormAccessCheckTest.php

book_breadcrumb_test.module in core/modules/book/tests/modules/book_breadcrumb_test/book_breadcrumb_test.module

Test module for testing the book module breadcrumb.

LatestRevisionCheckTest.php in core/modules/content_moderation/tests/src/Unit/LatestRevisionCheckTest.php

UserAccessControlHandler.php in core/modules/user/src/UserAccessControlHandler.php