Add acceptance test for noneditable failing grade range.

cms/djangoapps/contentstore/features/grading.feature

@@ -93,3 +93,9 @@ Feature: Course Grading
         And I press the "Save" notification button
         And I reload the page
         Then I see the highest grade range is "Good"
+
+    Scenario: User cannot edit failing grade range name
+        Given I have opened a new course in Studio
+        And I have populated the course
+        And I am viewing the grading settings
+        Then I cannot edit the "Fail" grade range

cms/djangoapps/contentstore/features/grading.py

@@ -4,6 +4,7 @@
 from lettuce import world, step
 from common import *
 from terrain.steps import reload_the_page
+from selenium.common.exceptions import InvalidElementStateException
 
 
 @step(u'I am viewing the grading settings')
@@ -130,6 +131,18 @@ def i_see_highest_grade_range(_step, range_name):
     grade = world.css_find(range_css).first
     assert grade.value == range_name
 
+
+@step(u'I cannot edit the "Fail" grade range$')
+def cannot_edit_fail(_step):
+    range_css = 'span.letter-grade'
+    ranges = world.css_find(range_css)
+    assert len(ranges) == 2
+    try:
+        ranges.last.value = 'Failure'
+        assert False, "Should not be able to edit failing range"
+    except InvalidElementStateException:
+        pass  # We should get this exception on failing to edit the element
+
 def get_type_index(name):
     name_id = '#course-grading-assignment-name'
     all_types = world.css_find(name_id)