Custom RbTemplateHandler fails in test, works in dev

I created a custom RbTemplateHandler:

    # in lib/rb_template_handler:
    class RbTemplateHandler < ActionView::TemplateHandler
      include ActionView::TemplateHandlers::Compilable
      def compile(template)
        template.source
      end
    end

that I load:

    # in config/environment.rb:
    ...
    ActionView::Template.register_template_handler(:rb, RbTemplateHandler)

and use:

    # in app/controllers/people_controller.rb:
    class PeopleController < ApplicationController
      def index
        @people = Person.all
        respond_to do |format|
          format.json
        end
      end
    end
    
    # in app/views/people/index.html.rb:
    @people.map |person|
      { :id => person.id, :to_s => person.to_s }
    end.to_json

In development mode, this works fine at first:

$ script/console development
>> app.get '/people'
=> 200
>> "[{\"id\":\"1\", \"to_s\":\"John\"},{\"id\":\"2\", \"to_s\":\"Sally\"}]"

A second call, however, fails (in a way reminiscent of #:

>> app.get '/people'
ThreadError: stopping only thread
note: use sleep to stop forever

And in test, it always fails due to a missing template:

    # in test/functional/people_controller_test.rb:
    class PeopleControllerTest < ActionController::TestCase

      def test_get_to_index
        get :index, :format => 'json'
        assert_equal "[{\"to_s\":\"John\"},{\"to_s\":\"Sally\"}]", @response.body
      end
  
    end

$ rake test:functionals
  1) Error:
test_get_to_index(PeopleControllerTest):
ActionView::MissingTemplate: Missing template people/index.erb in view path app/views
  app/controllers/people_controller.rb:4:in `index'
  /test/functional/people_controller_test.rb:6:in `test_get_to_index'