Various older spec test runners in tests/SpecTests allowed incompatible tests to be skipped as incomplete. The list of tests and the skip reason was maintained in the test code. This allowed us to keep test files in sync with the specifications repo and also avoid any manual modifications (e.g. adding skipReason).

It would be helpful to add this functionality to UnifiedSpecTest.

This came up via PHPLIB-645, since there are several CRUD tests that need to be skipped. It's likely that more tests will follow once other specs are converted to the unified format.