Last week, we had the author of TDD for a Shopping Website LiveProject. Friday at 11am Ranch time, Steven Solomon will be hosting a live TDD session just for us. See for the agenda and registration link
EJB is not as much in favor as it used to be, while JPA has become a lot more relevant. So, instead of the EJB exam, it might serve you better if you go for JPA exam.
HTH,
Paul.
However, I can tell that JPA exam requires knowledge of the EJB (for example, EJB transaction attributes, knowledge of Dependency Injection in Java EE classes, etc.)
It would be easier for you if you first take EJB exam, and then JPA exam.
Regards,
MZ
Exam 1Z0-817: Upgrade OCP Java 6, 7 and 8 to Java SE 11 Developer Study Guide and Quiz