fizzbuzz.rb

#!/usr/bin/env ruby
#-*- coding: utf-8 -*-
#
# This work is in the public domain.
#

class FizzBuzz
  def initialize(argument)
    if argument < 1
      throw InvalidArgumentError
    end
    @target = argument
  end

  def result
    result = []
    (1 .. @target).each do |i|
      tmp = (i % 3 == 0) ? "Fizz" : ""
      tmp += (i % 5 == 0) ? "Buzz" : ""
      result << (tmp == "" ? i : tmp)
    end
    result
  end
end

if __FILE__ == $0
  target = ARGV[0].to_i

  begin
    fizzbuzz = FizzBuzz.new(target)
  rescue
    abort "usage: #{$0} target_number"
  end

  fizzbuzz.result.each{|i| puts i }

else /rspec$/.match $0
  require 'rspec'

  describe "FizzBuzz.result" do
    subject { @result = FizzBuzz.new(20).result }
    it { subject.at(0).should == 1 }
    it { subject.at(1).should == 2 }
    it { subject.at(2).should == "Fizz" }
    it { subject.at(3).should == 4 }
    it { subject.at(4).should == "Buzz" }
    it { subject.at(5).should == "Fizz" }
    it { subject.at(6).should == 7 }

    it { subject.at(13).should == 14 }
    it { subject.at(14).should == "FizzBuzz" }
    it { subject.at(15).should == 16 }
  end

  describe "argument == 0" do
    subject { lambda{ FizzBuzz.new(0) } }
    it { should raise_error }
  end

  describe "argument < 0" do
    subject { lambda{ FizzBuzz.new(-1) } }
    it { should raise_error }
  end
end