Malcolm's method is a good one. It's very similar to the tester shown in Way Beyond Monochrome 2nd Ed, by Ralph Lambrecht & Chris Woodhouse, which is the one I built (with minor modification based on components I could obtain in the U.S. I spent a few additional $ to include a jig made from MDB material that holds my LF lenses mounted on lensboards in position in front of the sensor as well as holding the light source in a fixed position. I did this so as to hold everything constant except the selected shutter speed, so I could check each shutter setting on each of six lenses for consistency by firing three times at each setting. My initial tests, however, were done using a standard AC bulb of sufficient brightness, and it soon became obvious that the recorded trace had an overlying high frequency signal that added some difficulty in reading the trace precisely. Expanding the trace enough in Audacity, I found to my surprise that the overlying frequency was about 120Hz, rather than the anticipated 60 Hz for US power supply. I queried Chris about this and he explained that "it normally comes from the fact that any power supply that has a bridge rectifier will cause current bumps 120 x per second (50x2=100 Hz in the UK)." So the only way to avoid this is to use DC power (as instructed). Just thought this would be good to know for anyone thinking of building one.
