Matthias pointed me to a TCK issue in the Bean Validation related classes (BeanValidator, UIInput).
I've created some public static final booleans, used to determine @startup whether Bean Validation and Unified EL are available.
The reason to declare them as public was because they are shared between the "javax.faces.component" and "javax.faces.bean" packages, but it will probably cause TCK failures.
Solution: Refactor the environment related "constants" to a package-private class that exists in all necessary packages. This class might delegate the plumbing to the IMPL to prevent code duplication.
See the issue on the mailing list: