How to run multiple Rails unit tests at once

bundle exec ruby -I.:test -e "ARGV.each{|f| require f}" file1 file1

or:

find test -name '*_test.rb' | xargs -t bundle exec ruby -I.:test -e "ARGV.each{|f| require f}"

I ended up hacking this into my RakeFile myself like so:

Rake::TestTask.new(:fast) do |t|
  files = if ENV['TEST_FILES']
    ENV['TEST_FILES'].split(',')
  else
    FileList["test/unit/**/*_test.rb", "test/functional/**/*_test.rb", "test/integration/**/*_test.rb"]
  end

  t.libs << 'test'
  t.verbose = true
  t.test_files = files
end
Rake::Task['test:fast'].comment = "Runs unit/functional/integration tests (or a list of files in TEST_FILES) in one block"

Then I whipped up this bash function that allows you to call rt with an arbitrary list of test files. If there's just one file it runs it as ruby directly (this saves 8 seconds for my 50k loc app), otherwise it runs the rake task.

function rt {
  if [ $# -le 1 ] ; then
    ruby -Itest $1
  else
    test_files = ""
    while [ "$1" != "" ]; do
      if [ "$test_files" == "" ]; then
        test_files=$1
      else
        test_files="$test_files,$1"
      fi
      shift
    done
    rake test:fast TEST_FILES=$test_files
  fi
}