Yup. Log on at the start of the test. Then log the finish.
I recall having a test done on my VW T4 which ended up failing due to a number plate bulb, which they immediately replaced at the end of the test, logged into the system again and then passed it. I asked the tester why he couldn't just swap the bulb as it was a quick think to do.
2 reasons:. Not allowed to work on vehicle during test and if an inspector happened to be watching, it would mean trouble. And the test duration is timed and doing remedial work would end up with the test taking longer than expected, which would raise alarm bells (not literally!).
I love the idea of the CCTV in every MOT station connected to DVLA. Going to have a bank of people watching MOT testers all day in how many hundreds and maybe thousands of test stations? Gotta love the paranoia of some folk