強度確認

test.rb

class A
  def a
    "super"
  end
end

module B
  def a
    "module"
  end
end

module B2
  def a
    "module2"
  end
end

class C < A
  def a
    "direct"
  end

  include B
end

C.new.a #=> "direct"


class D < A
  include B
end

D.new.a #=> "module"

class E < A
  include B
  include B2
end

E.new.a #=> "module2"