slow_undef.rb

#!/usr/bin/env ruby

require 'benchmark'

def add_methods_to_a_module(m)
  1_000.times.map do |i|
    method_name = "method_#{i}"
    m.__send__(:define_method, method_name) {}
    method_name
  end
end

def include_into_other_modules(m, prefix)
  10.times do |i|
    m = Module.new do
      include m
    end

    # We assign the module to a const to make sure it's not garbage collected
    Object.const_set("Module_#{prefix}_#{i}", m)
  end
end

module_under_test = Module.new

10.times do |i|
  methods = add_methods_to_a_module(module_under_test)
  include_into_other_modules(module_under_test, i)

  time_to_remove_methods = Benchmark.realtime do
    methods.each do |m|
      module_under_test.__send__ :undef_method, m
    end
  end

  printf "Time to remove methods: %.2f\n", time_to_remove_methods
end