Percentage error output in tests

percentage_error.sh

#!/bin/bash

# Save stdout & stderr to individual files:
bundle exec rspec > >(tee stdout.log) 2> >(tee stderr.log >&2)

# Calculate the percentage:
wc -l stderr.log stdout.log \
  | ruby -e \
  'err, _, total = ARGF.map(&:to_f); puts "#{(err/total*100).round}% error output"'

# => XX% error output