learn_ruby_by_example.rb

#!/usr/bin/env ruby
# encoding: UTF-8
#
# LearnRubyByExample: 
#
# Ruby is a highly expressive programming language. 
# Testing software is an expressive way to communicate how it works.
#
# In the middle of a night awake for allergy and insomnia, and some days after the 1st _why day,
# I've tried to combine Ruby and testing to help teaching ruby with some goals in mind:
#
# - it should be easy to read for non-programmers
# - it should be based in examples
# - it should run as a test suite, so all examples should work like a charm
# - it should have a few requirements (test/unit) and size (1 file, < 50 LOC)
#
# To see it working, download this gist and run the examples suite below.
#
# If you like it, fork this gist and help spreading the Ruby love out there! :D

require 'test/unit'

class LearnRubyByExample
  
  module TestCaseTemplate
  
    def after(&code)
      @setup_code = code
    end
  
    def this_code(&code)
      instance_eval &@setup_code if @setup_code
      @last_result = code.call
    end
  
    def returns(expected)
      assert_equal expected, @last_result
    end
  
  end

  class TestCaseFactory
  
    def self.build(description)
      new_class_name = class_name(description)
      eval <<-CODE
        class #{new_class_name} < Test::Unit::TestCase
          include LearnRubyByExample::TestCaseTemplate
        end
        #{new_class_name}
      CODE
    end
  
    def self.class_name(string)
      string.gsub(/[^a-zA-Z]/,'_') + "TestCase"
    end
  
  end

end

class String
  
  def For_example(&code)
    new_test_case_class = LearnRubyByExample::TestCaseFactory.build(self)
    new_test_case_class.class_eval{ define_method "test #{self}", code }
  end
  alias :For_instance :For_example
  alias :i_e :For_example
end



# Thanks Matz, _why, fxn and all the nice and generous Ruby people.
#
# Copyright (c) 2010 Raul Murciano
# - web: http://raul.murciano.net
# - email: raul@murciano.net
# - twitter: @happywebcoder
# - code: http://github.com/raul
#
#
# 
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
# 
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
# 
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.



"In Ruby, everything is an object and has a class, even the numbers". For_example {
  
  this_code {
    1.class
  }
  returns Fixnum
}



"In Ruby, you can share code easily with modules". For_instance {
  
  after {
    
    module Singer
      def sing(lyrics)
        " ♫ ♬ #{lyrics}  ♫ ♬"
      end
    end
    
    class Tenor
      include Singer
    end
    
    class RockStar
      include Singer
    end
  }
  
  
  this_code {
    luciano = Tenor.new
    luciano.sing "La donna è mobileeee"
  } 
  returns " ♫ ♬ La donna è mobileeee  ♫ ♬"
  
  
  this_code {
    freddy = RockStar.new
    freddy.sing "Empty spaces - what are we living for?"
  }
  returns " ♫ ♬ Empty spaces - what are we living for?  ♫ ♬"
  
}



"In Ruby, you can redefine a method for an object without affecting its class". For_example {
  
  after {
    class Person
      def talk
        "Hi there!"
      end
    end
    
    @mike = Person.new
    @raul = Person.new
    
    def hi_guys
      [@mike.talk, @raul.talk]
    end
  }
  
  
  this_code{
    hi_guys
  }
  returns ["Hi there!", "Hi there!"]
  
  
  this_code{
    def @raul.talk
      "Hola!"
    end
    hi_guys
  }
  returns ["Hi there!", "Hola!"]
  
}