Depends on how you are setting it up and what you are looking to trial. It is possible to setup a RAP against a controller initially and then not require the controller after provisioning it, but it wouldn't be much of a trial from a functionality standpoint.
It would be possible to configure it with a virtual AP that is in bridged mode and where the Remote-AP Operation mode is "backup". The backup setting means the SSID will be available only when the RAP cannot contact its controller. The caveat is the SSID needs to be open or PSK based.
It would be similar to setting up a "hotel mode ssid" for RAPs. The following summarizes that setup:
https://arubanetworkskb.secure.force.com/pkb/articles/HowTo/R-32