19 files declare their use of EntityViewMode in Drupal 8

CKEditorIntegrationTest.php in core/modules/media/tests/src/FunctionalJavascript/CKEditorIntegrationTest.php

comment.module in core/modules/comment/comment.module

Enables users to comment on published content.

CommentIntegrationTest.php in core/modules/comment/tests/src/Kernel/CommentIntegrationTest.php

CommentInterfaceTest.php in core/modules/comment/tests/src/Functional/CommentInterfaceTest.php

DisplayApiTest.php in core/modules/field/tests/src/Kernel/DisplayApiTest.php

DisplayModeUpdateTest.php in core/modules/field/tests/src/Kernel/DisplayModeUpdateTest.php

EntityDisplayModeTest.php in core/modules/field_ui/tests/src/Functional/EntityDisplayModeTest.php

EntityDisplayTest.php in core/modules/field_ui/tests/src/Kernel/EntityDisplayTest.php

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

EntityViewModeResourceTestBase.php in core/tests/Drupal/FunctionalTests/Rest/EntityViewModeResourceTestBase.php

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

FieldRenderedEntityTest.php in core/modules/views/tests/src/Kernel/Handler/FieldRenderedEntityTest.php

FieldUIRouteTest.php in core/modules/field_ui/tests/src/Functional/FieldUIRouteTest.php

MediaEmbedFilterTestBase.php in core/modules/media/tests/src/Kernel/MediaEmbedFilterTestBase.php

media_library.post_update.php in core/modules/media_library/media_library.post_update.php

Post update functions for Media Library.

MigrateViewModesTest.php in core/modules/node/tests/src/Kernel/Migrate/d6/MigrateViewModesTest.php

MigrateViewModesTest.php in core/modules/field/tests/src/Kernel/Migrate/d7/MigrateViewModesTest.php

RollbackViewModesTest.php in core/modules/field/tests/src/Kernel/Migrate/d7/RollbackViewModesTest.php

RowUITest.php in core/modules/views_ui/tests/src/Functional/RowUITest.php