38 files declare their use of Yaml

addTourLegacyConfig.php in core/modules/tour/tests/fixtures/addTourLegacyConfig.php
Adds deprecated tour config for testing updates.
ckeditor5-3222756.php in core/modules/ckeditor5/tests/fixtures/update/ckeditor5-3222756.php
Test fixture.
ckeditor5-3259593.php in core/modules/ckeditor5/tests/fixtures/update/ckeditor5-3259593.php
Test fixture.
ConfigController.php in core/modules/config/src/Controller/ConfigController.php
ConfigExportUITest.php in core/modules/config/tests/src/Functional/ConfigExportUITest.php
ConfigImportUITest.php in core/modules/config/tests/src/Functional/ConfigImportUITest.php
ConfigInstallProfileUnmetDependenciesTest.php in core/modules/config/tests/src/Functional/ConfigInstallProfileUnmetDependenciesTest.php
ConfigManager.php in core/lib/Drupal/Core/Config/ConfigManager.php
ConfigSingleExportForm.php in core/modules/config/src/Form/ConfigSingleExportForm.php
ConfigSingleImportExportTest.php in core/modules/config/tests/src/Functional/ConfigSingleImportExportTest.php
ConfigSingleImportForm.php in core/modules/config/src/Form/ConfigSingleImportForm.php
DistributionProfileTest.php in core/tests/Drupal/FunctionalTests/Installer/DistributionProfileTest.php
DistributionProfileTranslationQueryTest.php in core/tests/Drupal/FunctionalTests/Installer/DistributionProfileTranslationQueryTest.php
DistributionProfileTranslationTest.php in core/tests/Drupal/FunctionalTests/Installer/DistributionProfileTranslationTest.php
drupal-8.action-3022401.php in core/modules/action/tests/fixtures/update/drupal-8.action-3022401.php
Contains database additions to for testing upgrade path for action settings.
DrupalFlushAllCachesInInstallerTest.php in core/tests/Drupal/FunctionalTests/Installer/DrupalFlushAllCachesInInstallerTest.php
EntityTypeWithoutViewsDataTest.php in core/modules/datetime_range/tests/src/Kernel/Views/EntityTypeWithoutViewsDataTest.php
FileStorage.php in core/lib/Drupal/Core/Config/FileStorage.php
FileStorageTest.php in core/tests/Drupal/KernelTests/Core/Config/Storage/FileStorageTest.php
FunctionalTestSetupTrait.php in core/lib/Drupal/Core/Test/FunctionalTestSetupTrait.php
GenerateThemeTest.php in core/tests/Drupal/Tests/Core/Command/GenerateThemeTest.php
HelpTopicDiscovery.php in core/modules/help_topics/src/HelpTopicDiscovery.php
HelpTopicTwigLoader.php in core/modules/help_topics/src/HelpTopicTwigLoader.php
InfoParserDynamic.php in core/lib/Drupal/Core/Extension/InfoParserDynamic.php
InstallerNonEnglishProfileWithoutLocaleModuleTest.php in core/tests/Drupal/FunctionalTests/Installer/InstallerNonEnglishProfileWithoutLocaleModuleTest.php
InstallerRouterTest.php in core/tests/Drupal/FunctionalTests/Installer/InstallerRouterTest.php
jsonapi.php in core/modules/jsonapi/tests/fixtures/update/jsonapi.php
Test fixture.
LibraryDiscoveryParser.php in core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php
MaintenanceThemeUpdateRegistryTest.php in core/modules/system/tests/src/Functional/Theme/MaintenanceThemeUpdateRegistryTest.php
ModuleInstaller.php in core/lib/Drupal/Core/Extension/ModuleInstaller.php
ModulesListFormWebTest.php in core/modules/system/tests/src/Functional/Form/ModulesListFormWebTest.php
multi_value_fields.php in core/modules/views/tests/fixtures/update/multi_value_fields.php
Text fixture.
SingleVisibleProfileTest.php in core/tests/Drupal/FunctionalTests/Installer/SingleVisibleProfileTest.php
ThemeUiTest.php in core/modules/system/tests/src/Functional/Theme/ThemeUiTest.php
TwigEnvironment.php in core/lib/Drupal/Core/Template/TwigEnvironment.php
YamlDiscovery.php in core/lib/Drupal/Core/Discovery/YamlDiscovery.php
YamlFileLoader.php in core/lib/Drupal/Core/DependencyInjection/YamlFileLoader.php
YamlTest.php in core/tests/Drupal/Tests/Core/Serialization/YamlTest.php

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