newless.rb

class After
  def worked?; true; end
end

module Newless
  module_function

  def newless(klass)
    method_name = klass.name.to_sym
    return if \
      Kernel.private_method_defined?(method_name) ||
      Kernel.public_method_defined?(method_name)
    Kernel.send :define_method, method_name do |*args|
      klass.new(*args)
    end
  end
end

ObjectSpace.each_object(Class) do |klass|
  Newless.newless klass
end

class Object
  def self.inherited(klass)
    Newless.newless klass
  end
end

class Before
  def worked?; true; end
end

require 'minitest/autorun'

class TestTest < MiniTest::Test
  def test_after
    assert After().worked?
  end

  def test_before
    assert Before().worked?
  end

  def test_doesnt_clobber_existing_methods
    assert Array(:foo) == [:foo]
  end
end