An IntegrationTest is one that spans multiple controllers and actions, tying them all together to ensure they work together as expected. It tests more completely than either unit or functional tests do, exercising the entire stack, from the dispatcher to the database.

At its simplest, you simply extend IntegrationTest and write your tests using the get/post methods:

require "#{File.dirname(__FILE__)}/test_helper"

class ExampleTest < ActionController::IntegrationTest
  fixtures :people

  def test_login
    # get the login page
    get "/login"
    assert_equal 200, status

    # post the login and follow through to the home page
    post "/login", :username => people(:jamis).username,
      :password => people(:jamis).password
    follow_redirect!
    assert_equal 200, status
    assert_equal "/home", path
  end
end

However, you can also have multiple session instances open per test, and even extend those instances with assertions and methods to create a very powerful testing DSL that is specific for your application. You can even reference any named routes you happen to have defined!

require "#{File.dirname(__FILE__)}/test_helper"

class AdvancedTest < ActionController::IntegrationTest
  fixtures :people, :rooms

  def test_login_and_speak
    jamis, david = login(:jamis), login(:david)
    room = rooms(:office)

    jamis.enter(room)
    jamis.speak(room, "anybody home?")

    david.enter(room)
    david.speak(room, "hello!")
  end

  private

    module CustomAssertions
      def enter(room)
        # reference a named route, for maximum internal consistency!
        get(room_url(:id => room.id))
        assert(...)
        ...
      end

      def speak(room, message)
        xml_http_request "/say/#{room.id}", :message => message
        assert(...)
        ...
      end
    end

    def login(who)
      open_session do |sess|
        sess.extend(CustomAssertions)
        who = people(who)
        sess.post "/login", :username => who.username,
          :password => who.password
        assert(...)
      end
    end
end