Testing EventMachine periodic timers

runner.rb

require 'eventmachine'

module Sample
  class Runner
    DEFAULT_INTERVAL_IN_SECS = 1

    def initialize(command, interval=DEFAULT_INTERVAL_IN_SECS)
      @command  = command
      @interval = interval
    end

    def run(&after_command)
      EventMachine.run {
        EventMachine::PeriodicTimer.new(interval) {
          command.run
          after_command.call if after_command
        }
      }
    end

    private

    attr_reader :command, :interval
  end # Runner
end # Sample

runner_spec.rb

gem 'minitest'
require 'minitest/autorun'
require_relative './runner'

describe Sample::Runner do
  describe '#run' do
    it 'runs a command' do
      command = Minitest::Mock.new
      runner  = Sample::Runner.new(command)

      command.expect :run, self

      runner.run { EventMachine.stop }
      command.verify
    end

    it 'runs the loop at the interval set at initialization' do
      interval_in_secs  = 0.5
      runner            = Sample::Runner.new(fake_command, interval_in_secs)
      
      before  = Time.now.to_i
      runner.run { EventMachine.stop }
      after   = Time.now.to_i

      (before - after < 1).must_equal true
    end

    it 'executes a block after running the command' do
      runner        = Sample::Runner.new(fake_command)
      timer_loops   = 0

      return_value  = runner.run { 
        timer_loops = timer_loops + 1
        EventMachine.stop if timer_loops > 1
      }

      timer_loops.must_equal 2
    end
  end

  def fake_command
    command = Object.new
    def command.run; self; end
    command
  end 
end # Sample::Runner