added first test for the PostType model

Author: Oaphi

app/models/category.rb

@@ -44,7 +44,7 @@ def update_activity(last_activity)
 
   # Gets categories appropriately scoped for a given user
   # @param user [User] user to check
-  # @return [ActiveRecord::Relation<category>]
+  # @return [ActiveRecord::Relation<Category>]
   def self.accessible_to(user)
     if user&.at_least_moderator?
       return Category.all

test/models/post_type_test.rb

@@ -0,0 +1,9 @@
+require 'test_helper'
+
+class PostTypeTest < ActiveSupport::TestCase
+  test 'system? should correctly determine if a type is a system type' do
+    assert_not post_types(:question).system?
+    assert post_types(:policy_doc).system?
+    assert post_types(:help_doc).system?
+  end
+end