During testing, the entire rack, with cased movements attached, is placed in the various positions, and moved into the hot and cold testing areas. Instead of trying to read the time on each face when the daily test results are recorded, in the past they took a photograph of each rack, including a reference timepiece in the photo. This would record the position of each second hand in the rack, at the same instant, and would make it possible to read the indicated time on each face to a fraction of a second, as well as documenting the correct time on the reference timepiece. The photographic negative would be read under magnification, and the test sheet for each movement would be filled out. Today, a laser scans across the rack and reads the position of each second hand, and the test results are stored as a computer file.
Automatic watches are wound once a day, by their crowns.
They are happier in real life, where they are constantly wound during the day by their rotors, and their mainspring tension stays fairly constant. The opposite is true for handwinds, which do slightly better in testing than they do in real life. Rather than absolute accuracy, which can be regulated easily if the watch runs slightly fast or slow, the most significant aim of COSC testing is to test for consistancy in different positions and temperatures. This is primarily a test of the balance and hairspring. I had a conversation about this with Walt O. once, and he said that the balance and hairspring are part of a module which is not taken apart even when the watch is serviced, so a watch that performs well in testing should do so as long as this is not tampered with.