Fixes #115

[pgrange]

We observed broken pipe output messages with bash_unit test in some environments: github CI and nix builds. The tests are passing but display this suspiscious error message.

@Pamplemousse has been able to reproduce them locally by trapping SIGPIPE:

  # trap '' SIGPIPE
  # ./bash_unit -p test_fail_fails tests/test_core.sh
  Running tests in tests/test_core.sh
          Running test_fail_fails ... /nix/store/11b3chszacfr9liy829xqknzp3q88iji-gnugrep-3.11/bin/grep: write error: Broken pipe
  SUCCESS ✓
  Overall result: SUCCESS ✓

From man, SIGPIPE appears when a process writes on a pipe with no reader. Looking at the problematic tests, we see that they all rely on a muted bash_unit with a stacktrace output being muted.

When we look at how the stacktrace is muted, the code was like this:

  notify_stack () { : ; }

And when we look at how the stacktrace is outputed by bash_unit we see the following code:

  stacktrace | notify_stack

So we have some process run by stacktrace that is piped to a void function, that is, no process on the right of this pipe is reading which makes it a good candidate to generate a SIGPIPE.

By replacing the muted notify_stack with the following code, the issue is solved:

  notify_stack  () { $CAT >/dev/null ; }