Test a block in Ruby

group_of_thingies.rb

class GroupOfThingies
  attr_accessor :thingies

  # Use like this:
  #
  #   group_of_thingies = GroupOfThingies.new
  #   group_of_thingies.each do |thing|
  #     puts "Check out this awesome thing: #{thing}!"
  #   end
  #
  # or you can exclude a thing
  #   
  #   group_of_thingies = GroupOfThingies.new
  #   group_of_thingies.each(:except => bad_thing) do |thing|
  #     puts "This is a good thing: #{thing}!"
  #   end
  #
  def each(options={})
    thingies.each do |thing|
      yield(thing) unless options[:except] == thing
    end
  end
end

group_of_thingies_spec.rb

describe GroupOfThingies do
  subject { described_class.new }

  context 'when an except case occurs' do
    before do
      subject.thingies = [:a]
    end

    it 'does not yield' do
      lambda { subject.each(:except => :a) {|a| raise } }.should_not raise_exception
    end
  end
end

This is a great solution. Simple and easy to follow. I can look at the spec and know what the code does.