The subject was covered by Richard Simpson in the October 2018 issue. Basically you will have to find an approved tester, usually in a model engineering society although some model boat clubs have qualified testers.
May be worth looking on the Model Engineer website for pointers. Your profile doesn't say which part of the world you come from.
There are two sets of acceptable tests for insurance and safety purposes. One is known as the Green Book and used by most model engineers. The Model Power Boat Association have their own rules which you can see here:
**LINK**
As explained in Richard's article, the Green Book is currently under revision and the new version will cover gas tanks as well as boilers.
There are several references to the Green Book online including this one:
**LINK**
An online search may also throw up some idea of where to find a tester in your area.
Colin
Edited By Colin Bishop on 22/10/2018 22:13:14