Minimal example about ruby 2.1.0 refinements

refinements_spec.rb

module MyRefinements
  refine Object do
    def nice_name
      "wow I am a #{self.class}"
    end
  end

  refine Hash do
    def foo
      "foo"
    end

    def empty?
      delete(:null)
      super
    end
  end

end

class MyClass
  using MyRefinements
  attr_reader :registry

  def nice_name; super; end

  def initialize(reg=Hash.new)
    @registry = reg
  end

  def reg_foo
    registry.foo
  end

  def empty?
    registry.empty?
  end
end

describe MyClass do
  it "should have a nice name" do
    expect(subject.nice_name).to eq "wow I am a MyClass"
  end

  let(:its_registry) { subject.registry }

  specify "our class can use refined classeso" do
    expect(subject.reg_foo).to eq("foo")
  end

  specify "but the refinement doesn't persist externally" do
    expect { its_registry.foo }.to raise_error(NoMethodError)
  end

  context "using super call in refinements" do
    subject { MyClass.new({ null: true}) }
    specify { expect(subject).to be_empty }
  end
end