i have taken all of the test,but it has been years back.the gas test was very difficult back then.it was made directly from the american gas association code book which was six volumes. but i here now it has been standardized dealing more with cooking equipment and troubleshooting gas related problems.
I have taken them all. Not a real tough. They are simple, but watch for the off the wall questions. Also, if I am not mistaken, CFESA is expensive from a small company level, by not really paying for itself. JMO. Good luck, you can get the study materials from amazon.com
"Fighting Ignorance since 1973 (Its taking longer than we thought)." The Straight Dope.
You can take all the test online through it. It is a lot cheaper if you work for a certified company.
They have a program that gets your started with the basic online test. Once you get past the online part you will take the proctored exam at the nearest commercial kitchen equipment service company that is registered. If you pass the test you will have a chance at an in-person interview the same day. After that interview your will have a chance to apply at other service companies in your area that have registered.