some_helper_test.rb

require 'test_helper'
require 'ostruct'

class SomeHelperTest < ActionView::TestCase
  tests SomeHelper

  context "pager" do
    setup { @total_pages = 10 }
    
    should "show pagination form" do
      get_pagination
      assert_select "form.pagination[action=/search][method=post]" do
        assert_select 'input[type=hidden][name=page]'
        assert_select 'input[type=submit][name=move_page][value=Previous]'
        assert_select 'input[type=submit][name=move_page][value=Next]'
        assert_select 'input[type=text][name=go_to_page]'
      end
    end
    
    should "add \"first\" class on the first page and disable previous button" do
      get_pagination(0)
      assert_select 'form.pagination.first'
      assert_select 'input[type=submit][value=Previous][disabled]'
    end
    
    should "add \"last\" class on the last page and disable next button" do
      get_pagination(@total_pages)
      assert_select 'form.pagination.last'
      assert_select 'input[type=submit][value=Next][disabled]'
    end
    
    should "not add \"first\" class or disable the previous button elsewhere" do
      get_pagination
      assert_select 'form.pagination.first', false
      assert_select 'input[type=submit][value=Previous][disabled]', false
    end
    
    should "not add \"last\" class or disable the next button elsewhere" do
      get_pagination
      assert_select 'form.pagination.last', false
      assert_select 'input[type=submit][value=Next][disabled]', false
    end
    
    should "display current page and total" do
      get_pagination(page = 5)
      assert_select 'form.pagination span.pages span', :text => "Page #{page + 1} of #{@total_pages + 1}"
    end
    
    should "include search parameters if they exist" do
      flexmock(self).should_receive(:create_hidden_fields_for_search_params).with_no_args.once.and_return('')
      get_pagination
    end
  end
  
  private
    def get_pagination(current = 5, search_params = {})
      # #pagination is the helper I'm testing.
      set_response_body(pagination(current, @total_pages))
    end
    
    def set_response_body(value)
      @response = OpenStruct.new(:body => value)
    end
end

test_helper.rb

# Monkeypatching so we can write tests for helpers.
class ActionView::TestCase::TestController < ActionController::Base
  attr_accessor :params
  
  # Save the current initialize method to call in the new initialize method below.
  alias :base_initialize :initialize # unless method_defined?(:base_initialize)
  
  def initialize
    base_initialize
    
    #Hack Hack Hack: TestCase doesn't have context of a current url so cheat a bit
    @params = {}
    send(:initialize_current_url)
  end
end