reduce test runner verbosity

# FIXME image diff

if !(diff ${outfile} ${masterfile} &>/dev/null); then

  echo

  print_error "ERROR: output files do not match:\n    - actual: ${outfile}\n    - master: ${masterfile}"

  echo

  print_error "ERROR: output files do not match"

  echo -e "If the modification is intended, fix by running:\n    cp ${outfile} ${masterfile}"

  echo

  diff ${outfile} ${masterfile}

  echo -e "To view the diff, run:\n    diff ${outfile} ${masterfile}"

  exit 1

fi