Switching between discussion threads take focus to bottom of the page.

TNL-1530

common/djangoapps/terrain/stubs/comments.py

@@ -100,7 +100,9 @@ class StubCommentsServiceHandler(StubHttpRequestHandler):
             self.send_response(404, content="404 Not Found")
 
     def do_threads(self):
-        self.send_json_response({"collection": [], "page": 1, "num_pages": 1})
+        threads = self.server.config.get('threads', {})
+        threads_data = [val for key, val in threads.items()]
+        self.send_json_response({"collection": threads_data, "page": 1, "num_pages": 1})
 
     def do_search_threads(self):
         self.send_json_response(self.server.config.get('search_result', {}))

common/static/coffee/src/discussion/views/discussion_thread_view.coffee

@@ -125,7 +125,7 @@ if Backbone?
           resp_limit: responseLimit if responseLimit
         $elem: elem
         $loading: elem
-        takeFocus: true
+        takeFocus: false
         complete: =>
           @responsesRequest = null
         success: (data, textStatus, xhr) =>

common/test/acceptance/fixtures/discussion.py

@@ -119,6 +119,16 @@ class SingleThreadViewFixture(DiscussionContentFixture):
         }
 
 
+class MultipleThreadFixture(DiscussionContentFixture):
+
+    def __init__(self, threads):
+        self.threads = threads
+
+    def get_config_data(self):
+        threads_list = {thread['id']: thread for thread in self.threads}
+        return {"threads": json.dumps(threads_list), "comments": '{}'}
+
+
 class UserProfileViewFixture(DiscussionContentFixture):
 
     def __init__(self, threads):

common/test/acceptance/pages/lms/discussion.py

@@ -341,6 +341,42 @@ class DiscussionTabSingleThreadPage(CoursePage):
         with self.thread_page._secondary_action_menu_open(".forum-thread-main-wrapper"):
             self._find_within(".forum-thread-main-wrapper .action-close").first.click()
 
+    @wait_for_js
+    def is_window_on_top(self):
+        """
+        Check if window's scroll is at top
+        """
+        return self.browser.execute_script("return $('html, body').offset().top") == 0
+
+    def _thread_is_rendered_successfully(self, thread_id):
+        return self.q(css=".discussion-article[data-id='{}']".format(thread_id)).visible
+
+    def click_and_open_thread(self, thread_id):
+        """
+        Click specific thread on the list.
+        """
+        thread_selector = "li[data-id='{}']".format(thread_id)
+        self.q(css=thread_selector).first.click()
+        EmptyPromise(
+            lambda: self._thread_is_rendered_successfully(thread_id),
+            "Thread has been rendered"
+        ).fulfill()
+
+    def check_threads_rendered_successfully(self, thread_count):
+        """
+        Count the number of threads available on page.
+        """
+        return len(self.q(css=".forum-nav-thread").results) == thread_count
+
+    def check_window_is_on_top(self):
+        """
+        Check window is on top of the page
+        """
+        EmptyPromise(
+            self.is_window_on_top,
+            "Window is on top"
+        ).fulfill()
+
 
 class InlineDiscussionPage(PageObject):
     url = None

common/test/acceptance/tests/discussion/test_discussion.py

@@ -30,7 +30,7 @@ from ...fixtures.discussion import (
     Response,
     Comment,
     SearchResult,
-)
+    MultipleThreadFixture)
 
 from .helpers import BaseDiscussionMixin
 
@@ -256,6 +256,61 @@ class DiscussionTabSingleThreadTest(BaseDiscussionTestCase, DiscussionResponsePa
         self.assertFalse(self.thread_page.is_show_comments_visible(response_id))
 
 
+@attr('shard_1')
+class DiscussionTabMultipleThreadTest(BaseDiscussionTestCase):
+    """
+    Tests for the discussion page with multiple threads
+    """
+    def setUp(self):
+        super(DiscussionTabMultipleThreadTest, self).setUp()
+        AutoAuthPage(self.browser, course_id=self.course_id).visit()
+        self.thread_count = 2
+        self.thread_ids = []
+        self.setup_multiple_threads(thread_count=self.thread_count)
+
+        self.thread_page_1 = DiscussionTabSingleThreadPage(
+            self.browser,
+            self.course_id,
+            self.discussion_id,
+            self.thread_ids[0]
+        )
+        self.thread_page_2 = DiscussionTabSingleThreadPage(
+            self.browser,
+            self.course_id,
+            self.discussion_id,
+            self.thread_ids[1]
+        )
+        self.thread_page_1.visit()
+
+    def setup_multiple_threads(self, thread_count):
+        threads = []
+        for i in range(thread_count):
+            thread_id = "test_thread_{}_{}".format(i, uuid4().hex)
+            thread_body = "Dummy Long text body." * 50
+            threads.append(
+                Thread(id=thread_id, commentable_id=self.discussion_id, body=thread_body),
+            )
+            self.thread_ids.append(thread_id)
+        view = MultipleThreadFixture(threads)
+        view.push()
+
+    def test_page_scroll_on_thread_change_view(self):
+        """
+        Check switching between threads changes the page to scroll to bottom
+        """
+        # verify threads are rendered on the page
+        self.assertTrue(
+            self.thread_page_1.check_threads_rendered_successfully(thread_count=self.thread_count)
+        )
+
+        # From the thread_page_1 open & verify next thread
+        self.thread_page_1.click_and_open_thread(thread_id=self.thread_ids[1])
+        self.assertTrue(self.thread_page_2.is_browser_on_page())
+
+        # Verify that window is on top of page.
+        self.thread_page_2.check_window_is_on_top()
+
+
 @attr('shard_1')
 class DiscussionOpenClosedThreadTest(BaseDiscussionTestCase):
     """