gistfile1.rbx

require "rubygems"
require "spec"

class AccountService
  def withdraw(account, amount)
    account.debit(amount)
  end

  def deposit(account, amount)
    account.credit(amount)
  end
end

class SimpleAccount
  attr_reader :balance
  
  def initialize(balance)
    @balance = balance
  end

  def debit(amount)
    @balance -= amount
  end

  def credit(amount)
    @balance += amount
  end
end

class SavingsAccount
  attr_reader :balance
  
  def initialize(balance)
    @balance = balance
  end

  def debit(amount)
    @balance -= (amount + 5)
  end
end

module RolePlay
  ROLE_GROUPS = []

  def role(role_name)
    ROLE_GROUPS << self
    SimpleAccount.new(200)
  end

  module ExampleGroupMethods
    def should_fulfill_role(role_name)
      candidate = instance
      Spec::Runner.configuration.after(:suite) do
        unless $generated_groups
          $generated_groups = true
          ROLE_GROUPS.each do |example_group|
            impl = example_group.instance_variable_get(:@_implementation)
            description = example_group.description
            example_group.class.describe("#{example_group.class.description} - Candidate #{candidate}") do
              define_method(:role) {|name| candidate }
              it(description) { instance_eval(&impl) }
            end
          end
          Spec::Runner.options.run_examples
        end
      end
    end
  end
end

Spec::Example::ExampleGroup.send :include, RolePlay
Spec::Example::ExampleGroup.extend RolePlay::ExampleGroupMethods
      
describe SavingsAccount do
  def self.instance
    SavingsAccount.new(123)
  end
  
  should_fulfill_role "account"
end

describe AccountService do
  before(:each) do
    @service = AccountService.new
    @account = role("account")    
  end
  
  it "should withdraw from an account" do
    puts "in account service withdraw"
    p @account
    
    beginning = @account.balance
    @service.withdraw @account, 50
    @account.balance.should < beginning
  end

  it "should deposit to the account" do
    puts "in account service deposit"
    p @account

    beginning = @account.balance
    @service.deposit @account, 50
    @account.balance.should > beginning
  end
end

class AccountReporter
  def initialize(account)
    @account = account
  end

  def report
    "balance: #{@account.balance}"
  end
end

describe AccountReporter do
  it "should report the balance of an account" do
    puts "in account reporter"
    account = role("account")
    p account
    AccountReporter.new(account).report.should =~ /^balance: (\d+)/
  end
end