random.rb

def self.get_random_quiz
  quiz_ids = Quiz.all.map(&:id) # simplified to use a symbol proc
  random_ids = quiz_ids.shuffle
  Quiz.find(random_ids.first)
end

# Misspelled, should be "Challenge"

it "retrieves a random quiz" do
  quiz_a = FactoryGirl.create(:quiz_A)
  quiz_b = FactoryGirl.create(:quiz_B)
  quiz_ids = [quiz_a.id, quiz_b.id] # ensure using the right ids
  Quiz.stub_chain(:all, :collect).and_return(quiz_ids) # do you really need to stub this? Why not use the database?
  quiz_ids.should_receive(:shuffle).and_return(quiz_ids.reverse)
  QuizChalengeBuilder.get_random_quiz.should eq(quiz_b) # changed due to difference in rand
end