gistfile1.rb

require "test_notifier/runner/rspec"
TestNotifier.default_notifier = :notify_send

class User
  attr_reader :name, :age
  def initialize(name, age)
    @name, @age = name, age
  end
end

class From
  def self.[] items
    From.new(items)
  end

  def initialize(items)
    @items = items
  end
 
  def where
    @items = @items.select { |item| yield item}
    self
  end
  
  def select
    @items.map { |item| yield item }
  end
end

describe From do
  
  it "return empty array when the list is empty" do
    users = []
    From[users].select{ |u| u.name }.should == []
  end
  
  context 'querying one user' do
    let(:users) {[User.new('foo', 23)]}
    it "return the name from an element from the list" do
      From[users].select{ |u| u.name }.should == ["foo"]
    end

    it "return the age from an element from the list" do
      From[users].select{ |u| u.age }.should == [23]
    end    
  end

  context 'querying many users' do
    let(:users) {[User.new('foo', 23), User.new('bar', 34)]}
             
    it "returns the different names for all the elements in the list" do
      From[users].select{ |u| u.name }.should == ['foo', 'bar']
    end

    it "filters the results by the where expression" do
      From[users].where{ |u| u.age == 23 }.select{ |u| u.name }.should == ['foo']
    end

    it "filters the results greater than an age" do
      From[users].where{ |u| u.age > 23 }.select{ |u| u.name }.should == ['bar']
    end

    it "filters the results lower than an age" do
      From[users].where{ |u| u.age < 24 }.select{ |u| u.name }.should == ['foo']
    end
  end

end