Hi @vlad,

here's a repository that reproduces the problem:

https://github.com/ptahchiev/hibernate-test-case-templates/tree/HHH-12480

The test-case works fine under java8, and fails under java9 with:
java.lang.ClassCastException: org.hibernate.bugs.JPAUnitTestCase$Child_$$_jvstef1_2 cannot be cast to org.hibernate.bugs.JPAUnitTestCase$SubChild