Check the visibility of private and protected mixined from module. Example from http://www.treibstofff.de/2009/08/07/ruby-visibility-of-private-and-protected-module-methods-when-mixed-into-a-class/

method_visibility_in_mixined_module.rb

module MyMethods
  def my_public_method
  puts "Public"
  end

  protected
  def my_protected_method
    puts "Protected"
  end

  private
  def my_private_method
    puts "Private"
  end
end

class MyClass
  include MyMethods

  def invoke_my_protected_method
    my_protected_method
  end

  def invoke_my_private_method
    my_private_method
  end
end

class MyInheritedClass < MyClass
  def invoke_my_protected_method_from_subclass
    my_protected_method
  end

  def invoke_my_private_method_from_subclass
    my_private_method
  end
end

mc = MyClass.new

mc.my_public_method

begin
  mc.my_protected_method
rescue NoMethodError
  puts "Unable to call a protected method."
end

begin
  mc.my_private_method
rescue NoMethodError
  puts "Unable to call a private method."
end

mc.invoke_my_protected_method
mc.invoke_my_private_method

mic = MyInheritedClass.new
mic.invoke_my_protected_method_from_subclass

begin
  mic.invoke_my_private_method
rescue NoMethodError
  puts "Unable to call a private method of the parent class."
end

##### OUTPUT

# Public
#
# Unable to call a protected method.
#
# Unable to call a private method.
#
# Protected
#
# Private
#
# Protected
#
# Private