Failing test with JPQL: from Employee e where e.contractType = org.hibernate.test.converter.QueryTest.ContractType.INTERNAL
I am not sure that query is correct (as ContractType enum is inner class for QueryTest class). If it is correct, problem leaves in select does not escape converted enum character.
Enum ContractType should be stored in database as single character code (field can have @Column(length = 1)). JPQL with restriction to some particular enum value, does not escape converted character (i.e. select x from XXX x where x.y=C, instead of select x from XXX x where x.y='C'.