I guess testing specifically for an exit code of 1 isn't as easy to remember.

  (grep -q notwanted /hay/stack ; test $? == 1) && echo "No violations found"

But you're right...the simpler format would do the wrong thing if, for example, the file didn't exist or had bad permissions or was a directory instead of a file.

Depends on what you mean by wrong. If the tests can’t run successfully because they detect an error or because they have an error, it still is a valuable signal to raise to the developer.

Consider what would happen if your unit test framework couldn’t compile the test files and failed with an error. Isn’t that also a test failure?