tmp.rb

def foo(collection)
  if collection.empty?
    collectionect.first
  else
    [ collection.first ] + foo_recurse( collection.rest )
  end
end

alias_method :foo_recurse, :foo

## spec:

it "should recurse on the rest of the items" do
  @obj.should_receive(:foo_recurse).with([2,3,4])
  @obj.foo([1,2,3,4])
end