raise_spec.rb

require 'rspec'

class Dummy
  attr_reader :arg

  def initialize(arg)
    @arg = arg
  end
end
describe 'raise' do
  context 'no arg' do
    subject { lambda { Dummy.new } }
    it { should raise_error }
  end

  context 'with arg' do
    subject { Dummy.new('arg') }
    its(:arg) { should eq 'arg' }
  end
end