quiz question types works with groups

fixes CNVS-20948

test plan:
  - make a quiz with multiple questions
    and a quiz group with questions of
    different types in it
  - ping the API endpoint for this quiz
    "api/v1/courses/:id/quizzes/:id"
  - the question_types array contains
    the types from the quiz group
    and the types of the non-nested
    questions

Change-Id: I647499707fa024a19fac564688653db3c9f9e4c7
Reviewed-on: https://gerrit.instructure.com/55993
Reviewed-by: Ryan Taylor <rtaylor@instructure.com>
Tested-by: Jenkins
QA-Review: Michael Hargiss <mhargiss@instructure.com>
Product-Review: Ryan Taylor <rtaylor@instructure.com>

app/models/quizzes/quiz.rb

@@ -552,9 +552,16 @@ class Quizzes::Quiz < ActiveRecord::Base
   # Lists all the question types available in this quiz
   def question_types
     return [] unless quiz_data
-    quiz_data.map do |question|
-      question["question_type"]
-    end.uniq
+
+    all_question_types = quiz_data.flat_map do |datum|
+      if datum["entry_type"] == "quiz_group"
+        datum["questions"].map{|q| q["question_type"]}
+      else
+        datum["question_type"]
+      end
+    end
+
+    all_question_types.uniq
   end
 
   def has_access_code

spec/models/quizzes/quiz_spec.rb

@@ -1066,6 +1066,25 @@ describe Quizzes::Quiz do
     end
   end
 
+  describe "#question_types" do
+    before :once do
+      @quiz = @course.quizzes.build :title => "test quiz", :hide_results => 'invalid'
+    end
+
+    it "returns an empty array when no quiz data" do
+      @quiz.stubs(:quiz_data).returns nil
+      expect(@quiz.question_types).to eq([])
+    end
+
+    it "returns quiz types of question in quiz groups" do
+      @quiz.stubs(:quiz_data).returns([
+        {"question_type" => "foo"},
+        {"entry_type" => "quiz_group", "questions" => [{"question_type" => "bar"},{"question_type" => "baz"}]}
+      ])
+      expect(@quiz.question_types).to eq(["foo", "bar", "baz"])
+    end
+  end
+
   describe "#has_file_upload_question?" do
 
     let(:quiz) { @course.quizzes.build title: 'File Upload Quiz' }