13 files declare their use of ContactForm in Drupal 8

ConfigTranslationListUiTest.php in core/modules/config_translation/tests/src/Functional/ConfigTranslationListUiTest.php

contact.post_update.php in core/modules/contact/contact.post_update.php

Post update functions for Contact.

ContactFieldsTest.php in core/modules/contact/tests/src/Kernel/Views/ContactFieldsTest.php

ContactFormResourceTestBase.php in core/modules/contact/tests/src/Functional/Rest/ContactFormResourceTestBase.php

ContactFormTest.php in core/modules/jsonapi/tests/src/Functional/ContactFormTest.php

ContactSitewideTest.php in core/modules/contact/tests/src/Functional/ContactSitewideTest.php

ContentEntityNullStorageTest.php in core/tests/Drupal/KernelTests/Core/Entity/ContentEntityNullStorageTest.php

demo_umami.profile in core/profiles/demo_umami/demo_umami.profile

Enables modules and site configuration for a demo_umami site installation.

MessageResourceTestBase.php in core/modules/contact/tests/src/Functional/Rest/MessageResourceTestBase.php

MessageTest.php in core/modules/jsonapi/tests/src/Functional/MessageTest.php

MigrateContactCategoryTest.php in core/modules/contact/tests/src/Kernel/Migrate/MigrateContactCategoryTest.php

standard.profile in core/profiles/standard/standard.profile

Enables modules and site configuration for a standard site installation.

StandardTest.php in core/profiles/standard/tests/src/Functional/StandardTest.php