16 files declare their use of Menu in Drupal 8

block.module in core/modules/block/block.module

Controls the visual building blocks a page is constructed with.

BlockXssTest.php in core/modules/block/tests/src/Functional/BlockXssTest.php

MenuAccessControlHandlerTest.php in core/modules/system/tests/src/Kernel/MenuAccessControlHandlerTest.php

MenuCacheTagsTest.php in core/modules/menu_ui/tests/src/Functional/MenuCacheTagsTest.php

MenuLinkContentDeleteFormTest.php in core/modules/menu_link_content/tests/src/Functional/MenuLinkContentDeleteFormTest.php

MenuLinksTest.php in core/modules/menu_link_content/tests/src/Kernel/MenuLinksTest.php

MenuResourceTestBase.php in core/modules/system/tests/src/Functional/Rest/MenuResourceTestBase.php

MenuStorageTest.php in core/modules/system/tests/src/Kernel/Menu/MenuStorageTest.php

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

MenuUiJavascriptTest.php in core/modules/menu_ui/tests/src/FunctionalJavascript/MenuUiJavascriptTest.php

MenuUiTest.php in core/modules/menu_ui/tests/src/Functional/MenuUiTest.php

MenuUninstallTest.php in core/modules/menu_ui/tests/src/Functional/MenuUninstallTest.php

menu_ui.module in core/modules/menu_ui/menu_ui.module

Allows administrators to customize the site's navigation menus.

MigrateMenuTest.php in core/modules/system/tests/src/Kernel/Migrate/d6/MigrateMenuTest.php

MigrateMenuTest.php in core/modules/system/tests/src/Kernel/Migrate/d7/MigrateMenuTest.php

SystemMenuBlockTest.php in core/modules/system/tests/src/Kernel/Block/SystemMenuBlockTest.php