temperature_test.rb

require 'test/unit'     
require 'rubygems'
require 'mocha'

class TemperatureSampler
  def initialize(sensor)
    @sensor = sensor
  end

  def average_temp
    total = (0...3).collect {
      @sensor.read_temperature
    }.inject { |i, s| i + s }
    total / 3.0
  end
end

class TestTemperatureSampler < Test::Unit::TestCase
  def test_sensor_can_average_three_temperature_readings
    sensor = mock()
    sensor.expects(:read_temperature).returns(10)#.times(3).
      #and_return(10, 12, 14)

    sampler = TemperatureSampler.new(sensor)
    #assert_equal 12, sampler.average_temp
  end
end