Gemfile

gem 'minitest'

safe_send.rb

class Object

  alias_method :unsafe_send, :send
  alias_method :safe_send, :public_send
  alias_method :send, :safe_send

end

safe_send_test.rb

require './safe_send'
require 'minitest/autorun'

class MyClass
  def my_public_method
    "Hello"
  end

  private

  def my_private_method
    "Get out of here!"
  end
end


describe MyClass do
  it "should allow me to call #my_public_method" do
    MyClass.new.my_public_method.must_equal "Hello"
  end

  it "should not allow me to call #my_private_method" do
    MyClass.new.my_public_method.must_equal "Hello"
  end

  it "should not allow me to call #my_private_method" do
    assert_raises(NoMethodError) {
      MyClass.new.my_private_method
    }
  end

  it "should not allow me to call #my_private_method using send" do
    assert_raises(NoMethodError) {
      MyClass.new.send(:my_private_method)
    }
  end
end

/Users/ej/.rvm/gems/ruby-2.1.1/gems/minitest-5.3.3/lib/minitest.rb:21:in `public_send': private method `attr_accessor' called for #<Class:Minitest> (NoMethodError)
    from /Users/ej/.rvm/gems/ruby-2.1.1/gems/minitest-5.3.3/lib/minitest.rb:21:in `<module:Minitest>'
    from /Users/ej/.rvm/gems/ruby-2.1.1/gems/minitest-5.3.3/lib/minitest.rb:9:in `<top (required)>'
    from /Users/ej/.rvm/gems/ruby-2.1.1/gems/minitest-5.3.3/lib/minitest/autorun.rb:8:in `require'
    from /Users/ej/.rvm/gems/ruby-2.1.1/gems/minitest-5.3.3/lib/minitest/autorun.rb:8:in `<top (required)>'
    from safe_send_test.rb:2:in `require'
    from safe_send_test.rb:2:in `<main>'