Live output from --show-output-of-passing-tests

[jglick]

Is your feature request related to a problem? Please describe.
--show-output-of-passing-tests displays test output but only after the test completes. For tests which normally take many minutes to complete, or which appear to be hung, it is therefore difficult to tell what is going on. For example you may be checked a build log in a CI system to see if your new test is actually progressing or got stuck somewhere, but there is no way to see that until it completes (or times out, or is aborted).

Example:

@test "incremental output" {
  for x in 0 1 2 3 4 5 6 7 8 9
  do
    date
    sleep 3
  done
}

run as

$ bats --show-output-of-passing-tests x.sh
x.sh
 ✓ incremental output
   Fri Jan 19 04:45:42 PM EST 2024
   Fri Jan 19 04:45:45 PM EST 2024
   Fri Jan 19 04:45:48 PM EST 2024
   Fri Jan 19 04:45:51 PM EST 2024
   Fri Jan 19 04:45:54 PM EST 2024
   Fri Jan 19 04:45:57 PM EST 2024
   Fri Jan 19 04:46:00 PM EST 2024
   Fri Jan 19 04:46:03 PM EST 2024
   Fri Jan 19 04:46:06 PM EST 2024
   Fri Jan 19 04:46:09 PM EST 2024

1 test, 0 failures

initially prints only the test name; the full output only appears 30s later, all at once.

Describe the solution you'd like
Output should be streamed to the bats stdout/stderr as it is processed.

Describe alternatives you've considered
tail -f /tmp/bats-run-<something>/bats.<something>.out can be used as a workaround, but the filenames are unpredictable, and you cannot use a wildcard because there are two *.out files, one of which is empty AFAICT.

[martin-schulze-vireso]

Implementing this would probably require deep changes, as the buffering happens on multiple levels.

Additionally, the formatters would need to be adapted, as their output is not consistent with this requirement.