gistfile1.txt

# Original: https://gist.github.com/otaviomedeiros/1950961
# Updated for new RSpec syntax

RSpec::Matchers.define :alias_from do |alias_method|
  match do |subject|
    begin
      subject.send(alias_method)
    rescue NoMethodError
      raise "expected alias_method from #{alias_method} to #{@original_method} but #{alias_method} is not defined"
    end

    subject.method(alias_method).eql?(subject.method(@original_method))
  end

  description do
    "delegate :#{@original_method} to :#{alias_method}"
  end

  failure_message do |text|
    "expected alias_method from #{alias_method} to #{@original_method}"
  end

  failure_message_when_negated do |text|
    "do not expected alias_method from #{alias_method} to #{@original_method}"
  end

  chain(:to) { |original_method| @original_method = original_method }
end