test.rb

require 'test/unit'

class A
  def a
  end
  def method_missing(*)
  end
end

class B < A
  def method_missing(*)
  end
end

class FooTest < Test::Unit::TestCase
  def setup
    @o = Object.new
  end

  def _test_method_name
    assert(!@o.respond_to?(:method_missing))
    assert A.new.respond_to?(:method_missing)
    assert B.new.respond_to?(:method_missing)
    B.send :remove_method, :method_missing
    assert A.new.respond_to?(:method_missing)
    assert B.new.respond_to?(:method_missing)
  end

  def test_2
    assert(!@o.respond_to?(:method_missing))
    assert A.new.respond_to?(:method_missing)
    assert B.new.respond_to?(:method_missing)
    A.send :remove_method, :method_missing
    assert !A.new.respond_to?(:method_missing)
    assert B.new.respond_to?(:method_missing)
  end
end


module FooBarBaz
  module Foo
    def foo_bar_baz
      2
    end
  end
  include Foo

  module Bar
    def foo_bar_baz
      super * 3
    end
  end
  include Bar

  module Baz
    def foo_bar_baz
      super * 7
    end
  end
  include Baz
end

o = Object.new
o.extend FooBarBaz
meta_o = class << o; self; end
p meta_o.ancestors
p o.foo_bar_baz