14 files declare their use of Workspace in Drupal 9

InstallUninstallTest.php in core/modules/system/tests/src/Functional/Module/InstallUninstallTest.php

PathWorkspacesTest.php in core/modules/workspaces/tests/src/Functional/PathWorkspacesTest.php

TestWorkspaceNegotiator.php in core/modules/workspaces/tests/modules/workspace_update_test/src/Negotiator/TestWorkspaceNegotiator.php

WorkspaceAccessTest.php in core/modules/workspaces/tests/src/Kernel/WorkspaceAccessTest.php

WorkspaceCacheContextTest.php in core/modules/workspaces/tests/src/Functional/WorkspaceCacheContextTest.php

WorkspaceContentModerationIntegrationTest.php in core/modules/content_moderation/tests/src/Functional/WorkspaceContentModerationIntegrationTest.php

WorkspaceCRUDTest.php in core/modules/workspaces/tests/src/Kernel/WorkspaceCRUDTest.php

WorkspaceIntegrationTest.php in core/modules/workspaces/tests/src/Kernel/WorkspaceIntegrationTest.php

WorkspacePermissionsTest.php in core/modules/workspaces/tests/src/Functional/WorkspacePermissionsTest.php

WorkspaceResourceTestBase.php in core/modules/workspaces/tests/src/Functional/EntityResource/WorkspaceResourceTestBase.php

workspaces.install in core/modules/workspaces/workspaces.install

Contains install, update and uninstall functions for the Workspaces module.

WorkspaceTestTrait.php in core/modules/workspaces/tests/src/Kernel/WorkspaceTestTrait.php

WorkspaceTestUtilities.php in core/modules/workspaces/tests/src/Functional/WorkspaceTestUtilities.php

WorkspaceViewTest.php in core/modules/workspaces/tests/src/Functional/WorkspaceViewTest.php