9 files declare their use of AssertHelperTrait

AssertHelperTrait.php in core/modules/simpletest/src/AssertHelperTrait.php
BookUninstallValidatorTest.php in core/modules/book/tests/src/Unit/BookUninstallValidatorTest.php
FieldUninstallValidatorTest.php in core/modules/field/tests/src/Unit/FieldUninstallValidatorTest.php
FilterUninstallValidatorTest.php in core/modules/filter/tests/src/Unit/FilterUninstallValidatorTest.php
ForumUninstallValidatorTest.php in core/modules/forum/tests/src/Unit/ForumUninstallValidatorTest.php
KernelTestBase.php in core/tests/Drupal/KernelTests/KernelTestBase.php
ModuleRequiredByThemesUninstallValidatorTest.php in core/tests/Drupal/Tests/Core/Extension/ModuleRequiredByThemesUninstallValidatorTest.php
RequiredModuleUninstallValidatorTest.php in core/tests/Drupal/Tests/Core/Extension/RequiredModuleUninstallValidatorTest.php
TestBase.php in core/modules/simpletest/src/TestBase.php

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