The other day a colleague asked whether or not it’s possible to have SimpleCov return a group that only contains uncommitted changes. The answer is yes! After some digging around, we found the following way: # in spec_helper.rb SimpleCov.start 'rails' do add_group 'Changed' do |source_file| `git ls-files --exclude-standard --others \ && git diff --name-only \ && git diff --name-only --cached`.split("\n").detect do |filename| source_file.filena...