I would also do something like tap your desk sharply with a pen right before you film the test, and make sure the audio track is aligned with video at that poin

I would also do something like tap your desk sharply with a pen right before you film the test, and make sure the audio track is aligned with video at that point. I have no idea how accurate A/V syncing is on say a smartphone, but that would be a bummer if that was completely throwing off the test.