If you’re interested in climbing, then no reason not to do the FTP test on a climb. That will probably make it easier to avoid traffic lights and junctions etc if there is a long enough climb near you 🙂
One word of warning - doing FTP tests is a skill itself, and not everyone masters it. I always get higher 20min power numbers in races and/or climbs than I do during a test, so don’t bother anymore - I just take my FTP from those events. Don’t feel that you have to do an FTP test to get your FTP, if that makes sense 🙂