Slow down an instance method by 1 second.

delay_method.rb

# Delay Foo#method by 1 second before
# executing its original implementation.
def delay_method(klass, method)
  sleeping_giant = Module.new do
    define_method(method) do |*args, &block|
      sleep 1
      super(*args, &block)
    end
  end

  klass.prepend(sleeping_giant)

  yield

  sleeping_giant.module_eval do
    remove_method method
  end
end

# class X
#   def foo
#     p(:x)
#   end
# end
#
# X.new.foo # fast
#
# delay_method(X, :foo) do
#   X.new.foo # slow
# end
#
# X.new.foo # fast again