> A unit test for a piece of code like this might be "Given that the time signature for the music is 3:4, the software puts 3:4 in the appropriate place on each

> A unit test for a piece of code like this might be "Given that the time signature for the music is 3:4, the software puts 3:4 in the appropriate place on each line of output". Don't you still have the same problem colomon described here, though? Testing your stated condition "the software puts 3:4 in the appropriate place on each line of output" still implies some form of image recognition on the graphical output.