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

class MockBlock
  def to_proc
    lambda { |*a| call(*a) }
  end
end

describe GroupOfThingies do
  subject { GroupOfThingies.new }

  describe 'with a bunch of thingies' do
    let(:mock_thing_1) { mock 'thing 1' }
    let(:mock_thing_2) { mock 'thing 2' }
    let(:mock_thing_3) { mock 'thing 3' }

    let(:thingies) { [mock_thing_1, mock_thing_2, mock_thing_3]}

    before do
      subject.thingies = thingies
    end

    it 'can iterate through all of them' do
      available_things = [mock_thing_1, mock_thing_2, mock_thing_3]

      block = MockBlock.new
      block.should_receive(:call).with(mock_thing_1).ordered
      block.should_receive(:call).with(mock_thing_2).ordered
      block.should_receive(:call).with(mock_thing_3).ordered

      subject.each(&block)
    end

    it 'can iterate through all of them, but can exclude one' do
      available_things = [mock_thing_1, mock_thing_3]

      block = MockBlock.new
      block.should_receive(:call).with(mock_thing_1).ordered
      block.should_not_receive(:call).with(mock_thing_2)
      block.should_receive(:call).with(mock_thing_3).ordered

      subject.each(:except => mock_thing_2, &block)
    end
  end

  describe 'when there are no thingies' do
    it 'returns an empty array when iterating' do
      subject.each { }.should == []
    end
  end
end