On Sun Mar 30, 2025 at 6:11 AM EDT, Phillip Wood wrote: > Thank you for adding a test. We have a helper function test_line_count > which provides a helpful debugging message if the comparison fails. > Using that and avoiding process substitutions we'd write > > sort head >sorted_head && > sort cmp >sorted_cmp && > comm -12 sorted_head sorted_cmp >actual && > test_line_count = 0 actual Thanks for that helper tip. I was just about to send a v2 when your message came in, so I'm getting that incorporated now. By the way, I had originally wanted to write test assertions that checked the actual number of commit ids returned from each of the two calls to rev-list - something like: git rev-list --X-only HEAD...cmp >file && test_line_count = N file But since I'm not very familiar with this test harness yet, I couldn't actually figure the correct value for N. It's not 1 (the commit made in my test body), and it's not 2 (that commit, plus the one from the setup case at the top of the file). Any appropriate higher value wasn't obvious. So I switched to what you saw in my v1. Maybe this "no commit ids in common" test is actually the stronger assertion?