Ruby rspec测试：tennis scorer

rspec_tennis_scorer.rb

#---
# Excerpted from "Programming Ruby", P210-214
# 运行测试：$ spec rspec_tennis_scorer.rb
#---
require "tennis_scorer"

describe TennisScorer, "basic scoring" do
  before(:each) do
    @ts = TennisScorer.new
  end

  it "should start with a score of 0-0" do
    @ts.score.should == "0-0"
  end

  it "should be 15-0 if the server wins a point" do
    @ts.give_point_to(:server)
    @ts.score.should == "15-0"
  end

  it "should be 0-15 if the receiver wins a point" do
    @ts.give_point_to(:receiver)
    @ts.score.should == "0-15"
  end

  it "should be 15-15 after they both win a point" do
    @ts.give_point_to(:receiver)
    @ts.give_point_to(:server)
    @ts.score.should == "15-15"
  end

end

tennis_scorer.rb

#---
# Excerpted from "Programming Ruby", P210-214
#---
class TennisScorer

  OPPOSITE_SIDE_OF_NET = {
    :server => :receiver,
    :receiver => :server
  }

  def initialize
    @score = { :server => 0, :receiver => 0 }
  end

  def score
    "#{@score[:server]*15}-#{@score[:receiver]*15}"
  end

  def give_point_to(player)
    other = OPPOSITE_SIDE_OF_NET[player]
    fail "Unknown player #{player}" unless other
    @score[player] += 1
  end
end