drone.io（OSS版）で並列テストを実行してビルド時間を削減する

pipeline:
  build:
    image: hoge/piyo
  commands:
    - RAILS_ENV=test bundle exec rspec ${TESTFOLDER}

matrix:
  TESTFOLDER:
    - spec/models
    - spec/requests

require 'fileutils'
require 'pathname'

class RandomDistSpec

  def initialize
    FileUtils.rm_rf("matrix_specs")
    @worker_num = 4
  end

  def copy_ruby_spec
    specs = Dir.glob("spec/**/*_spec.rb").shuffle
    copy specs
  end

  private
  def copy specs
    slice_num = (specs.size / @worker_num).ceil

    1.upto(@worker_num) do |i|
      FileUtils.mkdir_p("matrix_specs/#{i}") unless FileTest.exist?("matrix_specs/#{i}")

      files = specs.slice!(0, slice_num)
      files.each do |file|
        dir = Pathname(file).dirname.to_s
        FileUtils.mkdir_p "matrix_specs/#{i}/#{dir}"
        FileUtils.cp file, "matrix_specs/#{i}/#{file}"
      end
    end
  end
end

spec = RandomDistSpec.new
spec.copy_ruby_spec

matrix:
  TESTFOLDER:
    - matrix_specs/1
    - matrix_specs/2