gistfile1.txt

       def run(plan)
          step = next_step(plan)
          puts step
        end

        def next_step(plan)
          case plan
            when ExecutionPlan::Sequence
              step = check_plan(plan)
            when ExecutionPlan::Concurrence
              step = check_plan(plan)
            when RunStep
              step = check_step(plan)
            when true
              return true
            else
              raise ArgumentError, "Don't know how to run #{plan}"
            end

          return step
        end

        def check_plan(plan)
          plan.steps.each do |step|
            current_step = next_step(step)

            if current_step != true
              return current_step
            end
          end
          return true
        end

        def check_step(step)
          if %w[skipped success].include?(step.status)
            return true
          else
            return step
          end
        end