added tests covering CommentThread#remove_follower last activity bumping

Author: Oaphi

test/models/comment_thread_test.rb

@@ -16,9 +16,28 @@ class CommentThreadTest < ActiveSupport::TestCase
     end
   end
 
-  test 'last_activity should correctly get the thread\'s last activity date & time' do
+  test 'remove_follower should correctly bump last_activity' do
+    std_usr = users(:standard_user)
     thread = comment_threads(:without_activity)
+    assert_equal thread.created_at, thread.last_activity
+
+    thread.add_follower(std_usr)
+    thread.reload
+    last_activity_after_follow = thread.last_activity
+
+    thread.remove_follower(std_usr)
+    thread.reload
+    last_activity_after_unfollow = thread.last_activity
+    assert_operator last_activity_after_follow, '<', last_activity_after_unfollow
+
+    thread.remove_follower(std_usr)
+    thread.reload
+    last_activity_after_noop = thread.last_activity
+    assert_operator last_activity_after_unfollow, '<', last_activity_after_noop
+  end
 
+  test 'last_activity should correctly get the thread\'s last activity date & time' do
+    thread = comment_threads(:without_activity)
     assert_equal thread.created_at, thread.last_activity
 
     thread.update!(title: 'this should bump last_activity')