Hi there,
With regards to the reaction test, I can only say practice practice practice. All I had was the 4 practice sheets that the TOC gave to me before assessment, and I did them repeatedly until I felt I had got the hang of them. There are tests available online and possibly some linked through this forum somewhere.
With the interview, I'd imagine they would be scenario based i.e. give me an example of when you have done this. That and general questions about your ability to carry out the role, how you would adapt, and what you understand about the company (who owns it, its routes etc).
Regards,
D.