RSpec sample: Stubbing a Kernel method in a constructor

rspec_sample.rb

# Stubbing a Kernel method in a constructor

class Sample
  def initialize
    puts 'Hello world!'
  end
end

describe Sample do
  it '#initialize call puts' do
    Sample.module_eval do
      alias :original_initialize :initialize
      def initialize
        self.should_receive(:puts).once.with('Hello world')
        original_initialize
      end
    end
    begin
      Sample.new
    ensure
      Sample.module_eval do
        alias :initialize :original_initialize
      end
    end
  end
end