Tests

Foundation defines the future test layout but does not add real PHP fixtures.

Later layers may add:

• Lexer differential fixtures compared against token_get_all().
• Parser accept/reject fixtures compared against php -l.
• Runtime fixtures compared against the reference CLI.
• Imported or adapted .phpt tests from the pinned PHP 8.5.7 reference.

Expected results should be generated from the pinned reference PHP, not written from memory.