Resolve "Sort updated comments chronoligically"

Closes #167 (closed)

functional_tests/test_feedback_creation.py

 from django.test import LiveServerTestCase
 from selenium import webdriver
+from selenium.webdriver import ActionChains
 from selenium.webdriver.support.ui import WebDriverWait
 from selenium.webdriver.support import expected_conditions as ec
+from selenium.webdriver.common.by import By
 
 from core.models import UserAccount, Submission, FeedbackComment
 from functional_tests.util import (login, create_browser, reset_browser_after_test,
                                    go_to_subscription, wait_until_code_changes,
-                                   reconstruct_submission_code)
+                                   reconstruct_submission_code, wait_until_element_count_equals)
 from util import factory_boys as fact
 
 
@@ -223,6 +225,74 @@ class UntestedParent:
             self.assertEqual(0, submission_for_code.feedback.score)
             self.assertEqual(1, submission_for_code.feedback.feedback_lines.count())
 
+        def test_comments_are_sorted_by_last_updated(self):
+            self._login()
+            go_to_subscription(self)
+
+            code = reconstruct_submission_code(self)
+            self.browser.find_element_by_id('score-full').click()
+
+            # give feedback on first line
+            self.write_comments_on_lines([(1, 'first ever comment')])
+
+            submit_btn = self.browser.find_element_by_id('submit-feedback')
+            submit_btn.click()
+
+            WebDriverWait(self.browser, 10).until(
+                wait_until_code_changes(self, code)
+            )
+
+            reset_browser_after_test(self.browser, self.live_server_url)  # logs out user
+
+            user_snd = 'tutor_snd'
+            password = 'p'
+            fact.UserAccountFactory(username=user_snd, password=password)
+
+            login(self.browser, self.live_server_url, user_snd, password)
+            go_to_subscription(self, stage='validate')
+
+            self.write_comments_on_lines([(1, 'the second comment')])
+            self.browser.find_element_by_id('score-full').click()
+            self.browser.find_element_by_class_name('final-checkbox').click()
+            self.browser.find_element_by_id('submit-feedback').click()
+
+            sub_url = 'subscription/' + str(self.sub_type.pk) + '/ended'
+            WebDriverWait(self.browser, 10).until(ec.url_contains(sub_url))
+
+            reset_browser_after_test(self.browser, self.live_server_url)  # logs out user
+            self._login()
+
+            # goto history
+            self.browser.find_element_by_id('feedback').click()
+            feedback_entry = self.browser.find_element_by_class_name('feedback-row')
+            ActionChains(self.browser).move_to_element(feedback_entry).click().perform()
+
+            # validate that second comment is under the first comment
+            comments = self.browser.find_elements_by_class_name('dialog-box')
+            first_text = comments[0].find_element_by_class_name('message')
+            second_text = comments[1].find_element_by_class_name('message')
+
+            self.assertEqual(len(comments), 2)
+            self.assertEqual(first_text.text, 'first ever comment')
+            self.assertEqual(second_text.text, 'the second comment')
+
+            # give feedback on first line
+            self.write_comments_on_lines([(1, 'first comment updated')])
+            self.browser.find_element_by_id('score-full').click()
+            self.browser.find_element_by_id('submit-feedback').click()
+
+            WebDriverWait(self.browser, 5).until(
+                wait_until_element_count_equals(self, By.CLASS_NAME, "dialog-box", 2)
+            )
+
+            # validate that the edited first comment is under the second comment
+            comments = self.browser.find_elements_by_class_name('dialog-box')
+            first_text = comments[0].find_element_by_class_name('message')
+            second_text = comments[1].find_element_by_class_name('message')
+
+            self.assertEqual(first_text.text, 'the second comment')
+            self.assertEqual(second_text.text, 'first comment updated')
+
 
 class TestFeedbackCreationTutor(UntestedParent.TestFeedbackCreationGeneric):
     def setUp(self):