Update open-ended tests to load the module between 'requests'

Under normal operation, XModules are reloaded on each request from a
student. CombinedOpenEnded modules have code that runs at initialization
that validates the students state. These changes makes that code run
during several long-form unit tests (testing CombinedOpenEnded across
multiple 'requests').

These tests are marked as expectedFailure because they now exhibit the
same failures as observed in [LMS-1493] (namely, the students state gets
reset, because CombinedOpenEnded interprets system.ajax_url raising an
error as meaning that the problem definition and the student answers are
in conflict)

common/lib/xmodule/xmodule/open_ended_grading_classes/combined_open_ended_modulev1.py

@@ -93,7 +93,6 @@ class CombinedOpenEndedV1Module():
         Definition file should have one or many task blocks, a rubric block, and a prompt block.  See DEFAULT_DATA in combined_open_ended_module for a sample.
 
         """
-
         self.instance_state = instance_state
         self.display_name = instance_state.get('display_name', "Open Ended")
 

common/lib/xmodule/xmodule/tests/test_peer_grading.py

@@ -41,13 +41,16 @@ class PeerGradingModuleTest(unittest.TestCase, DummyModulestore):
     })
     save_dict.extend(('rubric_scores[]', val) for val in (0, 1))
 
+    def get_module_system(self, descriptor):
+        test_system = get_test_system()
+        test_system.open_ended_grading_interface = None
+        return test_system
+
     def setUp(self):
         """
         Create a peer grading module from a test system
         @return:
         """
-        self.test_system = get_test_system()
-        self.test_system.open_ended_grading_interface = None
         self.setup_modulestore(COURSE)
         self.peer_grading = self.get_module_from_location(self.problem_location, COURSE)
         self.coe = self.get_module_from_location(self.coe_location, COURSE)
@@ -173,13 +176,16 @@ class PeerGradingModuleScoredTest(unittest.TestCase, DummyModulestore):
         ["i4x", "edX", "open_ended", "peergrading", "PeerGradingScored"]
     )
 
+    def get_module_system(self, descriptor):
+        test_system = get_test_system()
+        test_system.open_ended_grading_interface = None
+        return test_system
+
     def setUp(self):
         """
         Create a peer grading module from a test system
         @return:
         """
-        self.test_system = get_test_system()
-        self.test_system.open_ended_grading_interface = None
         self.setup_modulestore(COURSE)
 
     def test_metadata_load(self):
@@ -213,12 +219,15 @@ class PeerGradingModuleLinkedTest(unittest.TestCase, DummyModulestore):
     coe_location = Location(["i4x", "edX", "open_ended", "combinedopenended",
                              "SampleQuestion"])
 
+    def get_module_system(self, descriptor):
+        test_system = get_test_system()
+        test_system.open_ended_grading_interface = None
+        return test_system
+
     def setUp(self):
         """
         Create a peer grading module from a test system.
         """
-        self.test_system = get_test_system()
-        self.test_system.open_ended_grading_interface = None
         self.setup_modulestore(COURSE)
 
     @property
@@ -270,14 +279,16 @@ class PeerGradingModuleLinkedTest(unittest.TestCase, DummyModulestore):
         else:
             pg_descriptor.get_required_module_descriptors = lambda: []
 
+        test_system = self.get_module_system(pg_descriptor)
+
         # Initialize the peer grading module.
         peer_grading = PeerGradingModule(
             pg_descriptor,
-            self.test_system,
+            test_system,
             self.field_data,
             self.scope_ids,
         )
-        self.test_system.xmodule_instance = peer_grading
+        test_system.xmodule_instance = peer_grading
 
         return peer_grading
 
@@ -384,13 +395,16 @@ class PeerGradingModuleTrackChangesTest(unittest.TestCase, DummyModulestore):
     mock_track_changes_problem = Mock(side_effect=[MockedTrackChangesProblem()])
     pgm_location = Location(["i4x", "edX", "open_ended", "peergrading", "PeerGradingSample"])
 
+    def get_module_system(self, descriptor):
+        test_system = get_test_system()
+        test_system.open_ended_grading_interface = None
+        return test_system
+
     def setUp(self):
         """
         Create a peer grading module from a test system
         @return:
         """
-        self.test_system = get_test_system()
-        self.test_system.open_ended_grading_interface = None
         self.setup_modulestore(COURSE)
         self.peer_grading = self.get_module_from_location(self.pgm_location, COURSE)
 

common/lib/xmodule/xmodule/tests/test_util_open_ended.py

@@ -78,7 +78,9 @@ class DummyModulestore(object):
     """
     A mixin that allows test classes to have convenience functions to get a module given a location
     """
-    get_test_system = get_test_system()
+
+    def get_module_system(self, descriptor):
+        raise NotImplementedError("Sub-tests must specify how to generate a module-system")
 
     def setup_modulestore(self, name):
         self.modulestore = XMLModuleStore(DATA_DIR, course_dirs=[name])
@@ -93,7 +95,7 @@ class DummyModulestore(object):
         if not isinstance(location, Location):
             location = Location(location)
         descriptor = self.modulestore.get_instance(course.id, location, depth=None)
-        descriptor.xmodule_runtime = self.test_system
+        descriptor.xmodule_runtime = self.get_module_system(descriptor)
         return descriptor
 
 # Task state for a module with self assessment then instructor assessment.