18 files declare their use of WorkflowInterface

AddModeration.php in core/modules/content_moderation/src/Plugin/ConfigAction/AddModeration.php
ContentModeration.php in core/modules/content_moderation/src/Plugin/WorkflowType/ContentModeration.php
ContentModerationConfigureEntityTypesForm.php in core/modules/content_moderation/src/Form/ContentModerationConfigureEntityTypesForm.php
ContentModerationTestTrait.php in core/modules/content_moderation/tests/src/Traits/ContentModerationTestTrait.php
content_moderation.module in core/modules/content_moderation/content_moderation.module
Contains content_moderation.module.
ModerationInformationTest.php in core/modules/content_moderation/tests/src/Unit/ModerationInformationTest.php
StateTransitionValidation.php in core/modules/content_moderation/src/StateTransitionValidation.php
StateTransitionValidationInterface.php in core/modules/content_moderation/src/StateTransitionValidationInterface.php
Upgrade6TestWithContentModeration.php in core/modules/migrate_drupal_ui/tests/src/Functional/d6/Upgrade6TestWithContentModeration.php
Upgrade7TestWithContentModeration.php in core/modules/migrate_drupal_ui/tests/src/Functional/d7/Upgrade7TestWithContentModeration.php
Workflow.php in core/modules/workflows/src/Entity/Workflow.php
WorkflowCustomAccessType.php in core/modules/workflows/tests/modules/workflow_type_test/src/Plugin/WorkflowType/WorkflowCustomAccessType.php
WorkflowStateDeleteForm.php in core/modules/workflows/src/Form/WorkflowStateDeleteForm.php
WorkflowStateTransitionOperationsAccessCheckTest.php in core/modules/workflows/tests/src/Unit/WorkflowStateTransitionOperationsAccessCheckTest.php
WorkflowTransitionDeleteForm.php in core/modules/workflows/src/Form/WorkflowTransitionDeleteForm.php
WorkflowTypeBase.php in core/modules/workflows/src/Plugin/WorkflowTypeBase.php
workflow_type_test.module in core/modules/workflows/tests/modules/workflow_type_test/workflow_type_test.module
WorkspacesContentModerationStateTest.php in core/modules/content_moderation/tests/src/Kernel/WorkspacesContentModerationStateTest.php

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