gistfile1.rb

namespace :test do
  Rake::TestTask.new(:master => "test:prepare") do |t|
    def t.file_list
      changed_since_checkin = silence_stderr { `git diff --name-only master` }.map { |path| path.chomp }

      models      = changed_since_checkin.select { |path| path =~ /app[\\\/]models[\\\/].*\.rb$/ }
      controllers = changed_since_checkin.select { |path| path =~ /app[\\\/]controllers[\\\/].*\.rb$/ }

      unit_tests       = models.map { |model| "test/unit/#{File.basename(model, '.rb')}_test.rb" }
      functional_tests = controllers.map { |controller| "test/functional/#{File.basename(controller, '.rb')}_test.rb" }

      unit_tests.uniq + functional_tests.uniq
    end

    t.libs << 'test'
  end
  Rake::Task['test:master'].comment = "Test changes for files changed in current branch (from master)"
end