diff --git a/cms/djangoapps/contentstore/tests/test_courseware_index.py b/cms/djangoapps/contentstore/tests/test_courseware_index.py
index 3866b7afd2..22b05eaff9 100644
--- a/cms/djangoapps/contentstore/tests/test_courseware_index.py
+++ b/cms/djangoapps/contentstore/tests/test_courseware_index.py
@@ -1,14 +1,11 @@
 """
 Testing indexing of the courseware as it is changed
 """
-
-
 import json
 import time
 from datetime import datetime
 from unittest import skip
 from unittest.mock import patch
-from uuid import uuid4
 
 import ddt
 import pytest
@@ -33,25 +30,14 @@ from openedx.core.djangoapps.models.course_details import CourseDetails
 from xmodule.library_tools import normalize_key_for_search
 from xmodule.modulestore import ModuleStoreEnum
 from xmodule.modulestore.django import SignalHandler, modulestore
-from xmodule.modulestore.edit_info import EditInfoMixin
-from xmodule.modulestore.inheritance import InheritanceMixin
-from xmodule.modulestore.mixed import MixedModuleStore
 from xmodule.modulestore.tests.django_utils import (
+    ModuleStoreTestCase,
     TEST_DATA_MONGO_MODULESTORE,
     TEST_DATA_SPLIT_MODULESTORE,
-    SharedModuleStoreTestCase
+    SharedModuleStoreTestCase,
 )
 from xmodule.modulestore.tests.factories import CourseFactory, ItemFactory, LibraryFactory
-from xmodule.modulestore.tests.mongo_connection import MONGO_HOST, MONGO_PORT_NUM
-from xmodule.modulestore.tests.utils import (
-    LocationMixin,
-    MixedSplitTestCase,
-    MongoContentstoreBuilder,
-    create_modulestore_instance
-)
 from xmodule.partitions.partitions import UserPartition
-from xmodule.tests import DATA_DIR
-from xmodule.x_module import XModuleMixin
 
 COURSE_CHILD_STRUCTURE = {
     "course": "chapter",
@@ -93,46 +79,9 @@ def create_large_course(store, load_factor):
     return course, child_count
 
 
-class MixedWithOptionsTestCase(MixedSplitTestCase):
+class MixedWithOptionsTestCase(ModuleStoreTestCase):
     """ Base class for test cases within this file """
-    HOST = MONGO_HOST
-    PORT = MONGO_PORT_NUM
-    DATABASE = 'test_mongo_%s' % uuid4().hex[:5]
-    COLLECTION = 'modulestore'
-    ASSET_COLLECTION = 'assetstore'
-    DEFAULT_CLASS = 'xmodule.hidden_module.HiddenDescriptor'
-    RENDER_TEMPLATE = lambda t_n, d, ctx=None, nsp='main': ''
-    modulestore_options = {
-        'default_class': DEFAULT_CLASS,
-        'fs_root': DATA_DIR,
-        'render_template': RENDER_TEMPLATE,
-        'xblock_mixins': (EditInfoMixin, InheritanceMixin, LocationMixin, XModuleMixin),
-    }
-    DOC_STORE_CONFIG = {
-        'host': HOST,
-        'port': PORT,
-        'db': DATABASE,
-        'collection': COLLECTION,
-        'asset_collection': ASSET_COLLECTION,
-    }
-    OPTIONS = {
-        'stores': [
-            {
-                'NAME': 'draft',
-                'ENGINE': 'xmodule.modulestore.mongo.draft.DraftModuleStore',
-                'DOC_STORE_CONFIG': DOC_STORE_CONFIG,
-                'OPTIONS': modulestore_options
-            },
-            {
-                'NAME': 'split',
-                'ENGINE': 'xmodule.modulestore.split_mongo.split_draft.DraftVersioningModuleStore',
-                'DOC_STORE_CONFIG': DOC_STORE_CONFIG,
-                'OPTIONS': modulestore_options
-            },
-        ],
-        'xblock_mixins': modulestore_options['xblock_mixins'],
-    }
-
+    CREATE_USER = False
     INDEX_NAME = None
 
     def setup_course_base(self, store):
@@ -155,18 +104,10 @@ class MixedWithOptionsTestCase(MixedSplitTestCase):
 
     def _perform_test_using_store(self, store_type, test_to_perform):
         """ Helper method to run a test function that uses a specific store """
-        with MongoContentstoreBuilder().build() as contentstore:
-            store = MixedModuleStore(
-                contentstore=contentstore,
-                create_modulestore_instance=create_modulestore_instance,
-                mappings={},
-                **self.OPTIONS
-            )
-            self.addCleanup(store.close_all_connections)
-
-            with store.default_store(store_type):
-                self.setup_course_base(store)
-                test_to_perform(store)
+        store = modulestore()
+        with store.default_store(store_type):
+            self.setup_course_base(store)
+            test_to_perform(store)
 
     def publish_item(self, store, item_location):
         """ publish the item at the given location """
@@ -190,6 +131,7 @@ class TestCoursewareSearchIndexer(MixedWithOptionsTestCase):
     """ Tests the operation of the CoursewareSearchIndexer """
 
     WORKS_WITH_STORES = (ModuleStoreEnum.Type.mongo, ModuleStoreEnum.Type.split)
+    ENABLED_SIGNALS = ['course_deleted']
 
     def setUp(self):
         super().setUp()
@@ -264,11 +206,8 @@ class TestCoursewareSearchIndexer(MixedWithOptionsTestCase):
 
     def _test_indexing_course(self, store):
         """ indexing course tests """
-        response = self.search()
-        self.assertEqual(response["total"], 0)
-
         # Only published modules should be in the index
-        added_to_index = self.reindex_course(store)
+        added_to_index = self.reindex_course(store)  # This reindex may not be necessary (it may already be indexed)
         self.assertEqual(added_to_index, 3)
         response = self.search()
         self.assertEqual(response["total"], 3)
@@ -311,17 +250,15 @@ class TestCoursewareSearchIndexer(MixedWithOptionsTestCase):
         Test that course will also be delete from search_index after course deletion.
         """
         self.searcher = SearchEngine.get_search_engine(CourseAboutSearchIndexer.INDEX_NAME)
-        response = self.search()
-        self.assertEqual(response["total"], 0)
-
-        # index the course in search_index
+        # index the course in search_index (it may already be indexed)
         self.reindex_course(store)
         response = self.search()
         self.assertEqual(response["total"], 1)
 
         # delete the course and look course in search_index
-        modulestore().delete_course(self.course.id, ModuleStoreEnum.UserID.test)
-        self.assertIsNone(modulestore().get_course(self.course.id))
+        store.delete_course(self.course.id, ModuleStoreEnum.UserID.test)
+        self.assertIsNone(store.get_course(self.course.id))
+        # Now, because of contentstore.signals.handlers.listen_for_course_delete, the index should already be updated:
         response = self.search()
         self.assertEqual(response["total"], 0)
 
@@ -776,6 +713,7 @@ class TestTaskExecution(SharedModuleStoreTestCase):
             self.assertFalse(mock_index.called)
 
 
+@pytest.mark.django_db
 @ddt.ddt
 class TestLibrarySearchIndexer(MixedWithOptionsTestCase):
     """ Tests the operation of the CoursewareSearchIndexer """
@@ -929,7 +867,7 @@ class GroupConfigurationSearchMongo(CourseTestCase, MixedWithOptionsTestCase):
     """
     Tests indexing of content groups on course modules using mongo modulestore.
     """
-
+    CREATE_USER = True
     MODULESTORE = TEST_DATA_MONGO_MODULESTORE
     INDEX_NAME = CoursewareSearchIndexer.INDEX_NAME
 
diff --git a/common/lib/pytest.ini b/common/lib/pytest.ini
index 93c230eab2..bed2897487 100644
--- a/common/lib/pytest.ini
+++ b/common/lib/pytest.ini
@@ -1,5 +1,6 @@
 [pytest]
-DJANGO_SETTINGS_MODULE = openedx.tests.settings
+# Use the LMS settings for these tests; should work with CMS just as well though:
+DJANGO_SETTINGS_MODULE = lms.envs.test
 addopts = --nomigrations --reuse-db --durations=20 --json-report --json-report-omit keywords streams collectors log traceback tests --json-report-file=none
 # Enable default handling for all warnings, including those that are ignored by default;
 # but hide rate-limit warnings (because we deliberately don't throttle test user logins)
diff --git a/common/lib/xmodule/xmodule/modulestore/django.py b/common/lib/xmodule/xmodule/modulestore/django.py
index d96f8ee428..0be451cc41 100644
--- a/common/lib/xmodule/xmodule/modulestore/django.py
+++ b/common/lib/xmodule/xmodule/modulestore/django.py
@@ -265,7 +265,7 @@ def create_modulestore_instance(
         _options['create_modulestore_instance'] = create_modulestore_instance
 
     if issubclass(class_, BranchSettingMixin):
-        _options['branch_setting_func'] = _get_modulestore_branch_setting
+        _options.setdefault('branch_setting_func', _get_modulestore_branch_setting)
 
     if HAS_USER_SERVICE and not user_service:
         xb_user_service = DjangoXBlockUserService(get_current_user())
diff --git a/common/lib/xmodule/xmodule/modulestore/split_mongo/mongo_connection.py b/common/lib/xmodule/xmodule/modulestore/split_mongo/mongo_connection.py
index d2ead8e8ca..c868ee89f2 100644
--- a/common/lib/xmodule/xmodule/modulestore/split_mongo/mongo_connection.py
+++ b/common/lib/xmodule/xmodule/modulestore/split_mongo/mongo_connection.py
@@ -12,6 +12,7 @@ import zlib
 from contextlib import contextmanager
 from time import time
 
+from django.core.cache import caches, InvalidCacheBackendError
 import pymongo
 import pytz
 from mongodb_proxy import autoretry_read
@@ -22,11 +23,6 @@ from xmodule.modulestore import BlockData
 from xmodule.modulestore.split_mongo import BlockKey
 from xmodule.mongo_utils import connect_to_mongodb, create_collection_index
 
-try:
-    from django.core.cache import caches, InvalidCacheBackendError
-    DJANGO_AVAILABLE = True
-except ImportError:
-    DJANGO_AVAILABLE = False
 
 log = logging.getLogger(__name__)
 
@@ -198,11 +194,10 @@ class CourseStructureCache:
     """
     def __init__(self):
         self.cache = None
-        if DJANGO_AVAILABLE:
-            try:
-                self.cache = get_cache('course_structure_cache')
-            except InvalidCacheBackendError:
-                pass
+        try:
+            self.cache = get_cache('course_structure_cache')
+        except InvalidCacheBackendError:
+            pass
 
     def get(self, key, course_context=None):
         """Pull the compressed, pickled struct data from cache and deserialize."""
diff --git a/common/lib/xmodule/xmodule/modulestore/tests/django_utils.py b/common/lib/xmodule/xmodule/modulestore/tests/django_utils.py
index 9aa56b83ec..38912a4354 100644
--- a/common/lib/xmodule/xmodule/modulestore/tests/django_utils.py
+++ b/common/lib/xmodule/xmodule/modulestore/tests/django_utils.py
@@ -46,7 +46,7 @@ class StoreConstructors:
     draft, split = list(range(2))
 
 
-def mixed_store_config(data_dir, mappings, store_order=None):
+def mixed_store_config(data_dir, mappings, store_order=None, modulestore_options=None):
     """
     Return a `MixedModuleStore` configuration, which provides
     access to both Mongo-backed courses.
@@ -71,9 +71,17 @@ def mixed_store_config(data_dir, mappings, store_order=None):
     if store_order is None:
         store_order = [StoreConstructors.draft, StoreConstructors.split]
 
+    options = {
+        'default_class': 'xmodule.hidden_module.HiddenDescriptor',
+        'fs_root': data_dir,
+        'render_template': 'common.djangoapps.edxmako.shortcuts.render_to_string',
+    }
+    if modulestore_options:
+        options.update(modulestore_options)
+
     store_constructors = {
-        StoreConstructors.split: split_mongo_store_config(data_dir)['default'],
-        StoreConstructors.draft: draft_mongo_store_config(data_dir)['default'],
+        StoreConstructors.split: split_mongo_store_config(options)['default'],
+        StoreConstructors.draft: draft_mongo_store_config(options)['default'],
     }
 
     store = {
@@ -88,17 +96,10 @@ def mixed_store_config(data_dir, mappings, store_order=None):
     return store
 
 
-def draft_mongo_store_config(data_dir):
+def draft_mongo_store_config(modulestore_options):
     """
     Defines default module store using DraftMongoModuleStore.
     """
-
-    modulestore_options = {
-        'default_class': 'xmodule.hidden_module.HiddenDescriptor',
-        'fs_root': data_dir,
-        'render_template': 'common.djangoapps.edxmako.shortcuts.render_to_string'
-    }
-
     store = {
         'default': {
             'NAME': 'draft',
@@ -116,16 +117,10 @@ def draft_mongo_store_config(data_dir):
     return store
 
 
-def split_mongo_store_config(data_dir):
+def split_mongo_store_config(modulestore_options):
     """
     Defines split module store.
     """
-    modulestore_options = {
-        'default_class': 'xmodule.hidden_module.HiddenDescriptor',
-        'fs_root': data_dir,
-        'render_template': 'common.djangoapps.edxmako.shortcuts.render_to_string',
-    }
-
     store = {
         'default': {
             'NAME': 'draft',
@@ -207,6 +202,16 @@ TEST_DATA_SPLIT_MODULESTORE = functools.partial(
     store_order=[StoreConstructors.split, StoreConstructors.draft]
 )
 
+# Tests that use mixed modulestore and split, but don't load/use draft modulestore.
+# This also enables "draft preferred" mode, like Studio.
+TEST_DATA_ONLY_SPLIT_MODULESTORE_DRAFT_PREFERRED = functools.partial(
+    mixed_store_config,
+    mkdtemp_clean(),
+    {},
+    store_order=[StoreConstructors.split],
+    modulestore_options={'branch_setting_func': lambda: ModuleStoreEnum.Branch.draft_preferred},
+)
+
 
 class SignalIsolationMixin:
     """
diff --git a/common/lib/xmodule/xmodule/modulestore/tests/test_mixed_modulestore.py b/common/lib/xmodule/xmodule/modulestore/tests/test_mixed_modulestore.py
index 653dad78e6..27b014a3a1 100644
--- a/common/lib/xmodule/xmodule/modulestore/tests/test_mixed_modulestore.py
+++ b/common/lib/xmodule/xmodule/modulestore/tests/test_mixed_modulestore.py
@@ -51,13 +51,12 @@ from xmodule.modulestore.tests.factories import check_exact_number_of_calls, che
 from xmodule.modulestore.tests.mongo_connection import MONGO_HOST, MONGO_PORT_NUM
 from xmodule.modulestore.tests.test_asides import AsideTestType
 from xmodule.modulestore.tests.utils import (
-    LocationMixin,
     MongoContentstoreBuilder,
     create_modulestore_instance,
     mock_tab_from_json
 )
 from xmodule.modulestore.xml_exporter import export_course_to_xml
-from xmodule.modulestore.xml_importer import import_course_from_xml
+from xmodule.modulestore.xml_importer import LocationMixin, import_course_from_xml
 from xmodule.tests import DATA_DIR, CourseComparisonTest
 from xmodule.x_module import XModuleMixin
 
diff --git a/common/lib/xmodule/xmodule/modulestore/tests/test_mongo.py b/common/lib/xmodule/xmodule/modulestore/tests/test_mongo.py
index 08da4cfa75..f4bbbfdbb1 100644
--- a/common/lib/xmodule/xmodule/modulestore/tests/test_mongo.py
+++ b/common/lib/xmodule/xmodule/modulestore/tests/test_mongo.py
@@ -35,9 +35,9 @@ from xmodule.modulestore.inheritance import InheritanceMixin
 from xmodule.modulestore.mongo import MongoKeyValueStore
 from xmodule.modulestore.mongo.base import as_draft
 from xmodule.modulestore.tests.mongo_connection import MONGO_HOST, MONGO_PORT_NUM
-from xmodule.modulestore.tests.utils import LocationMixin, mock_tab_from_json
+from xmodule.modulestore.tests.utils import mock_tab_from_json
 from xmodule.modulestore.xml_exporter import export_course_to_xml
-from xmodule.modulestore.xml_importer import import_course_from_xml, perform_xlint
+from xmodule.modulestore.xml_importer import LocationMixin, import_course_from_xml, perform_xlint
 from xmodule.tests import DATA_DIR
 from xmodule.x_module import XModuleMixin
 
diff --git a/common/lib/xmodule/xmodule/modulestore/tests/test_semantics.py b/common/lib/xmodule/xmodule/modulestore/tests/test_semantics.py
index e5fcfbc10f..d74d9f4cc4 100644
--- a/common/lib/xmodule/xmodule/modulestore/tests/test_semantics.py
+++ b/common/lib/xmodule/xmodule/modulestore/tests/test_semantics.py
@@ -19,7 +19,11 @@ from xmodule.modulestore import ModuleStoreEnum
 from xmodule.modulestore.draft_and_published import DIRECT_ONLY_CATEGORIES
 from xmodule.modulestore.exceptions import ItemNotFoundError
 from xmodule.modulestore.tests.factories import CourseFactory
-from xmodule.modulestore.tests.utils import SPLIT_MODULESTORE_SETUP, MongoModulestoreBuilder, PureModulestoreTestCase
+from xmodule.modulestore.tests.django_utils import (
+    ModuleStoreTestCase,
+    TEST_DATA_MONGO_MODULESTORE,
+    TEST_DATA_SPLIT_MODULESTORE,
+)
 
 DETACHED_BLOCK_TYPES = dict(XBlock.load_tagged_classes('detached'))
 
@@ -40,7 +44,7 @@ class AsideTest(XBlockAside):
 
 
 @ddt.ddt
-class DirectOnlyCategorySemantics(PureModulestoreTestCase):
+class DirectOnlyCategorySemantics(ModuleStoreTestCase):
     """
     Verify the behavior of Direct Only items
     blocks intended to store snippets of course content.
@@ -377,8 +381,8 @@ class DirectOnlyCategorySemantics(PureModulestoreTestCase):
                 fields={'data': child_data},
             )
 
-        if child_published:
-            self.store.publish(child_usage_key, ModuleStoreEnum.UserID.test)
+            if child_published:
+                self.store.publish(child_usage_key, ModuleStoreEnum.UserID.test)
 
         self.assertCoursePointsToBlock(block_usage_key)
 
@@ -417,7 +421,7 @@ class TestSplitDirectOnlyCategorySemantics(DirectOnlyCategorySemantics):
     """
     Verify DIRECT_ONLY_CATEGORY semantics against the SplitMongoModulestore.
     """
-    MODULESTORE = SPLIT_MODULESTORE_SETUP
+    MODULESTORE = TEST_DATA_SPLIT_MODULESTORE
     __test__ = True
 
     @ddt.data(*TESTABLE_BLOCK_TYPES)
@@ -451,5 +455,5 @@ class TestMongoDirectOnlyCategorySemantics(DirectOnlyCategorySemantics):
     """
     Verify DIRECT_ONLY_CATEGORY semantics against the MongoModulestore
     """
-    MODULESTORE = MongoModulestoreBuilder()
+    MODULESTORE = TEST_DATA_MONGO_MODULESTORE
     __test__ = True
diff --git a/common/lib/xmodule/xmodule/modulestore/tests/test_split_modulestore.py b/common/lib/xmodule/xmodule/modulestore/tests/test_split_modulestore.py
index 8117b2c331..1739f48761 100644
--- a/common/lib/xmodule/xmodule/modulestore/tests/test_split_modulestore.py
+++ b/common/lib/xmodule/xmodule/modulestore/tests/test_split_modulestore.py
@@ -19,6 +19,7 @@ from opaque_keys.edx.locator import BlockUsageLocator, CourseKey, CourseLocator,
 from path import Path as path
 from xblock.fields import Reference, ReferenceList, ReferenceValueDict
 
+from openedx.core.djangolib.testing.utils import CacheIsolationMixin
 from openedx.core.lib import tempdir
 from openedx.core.lib.tests import attr
 from xmodule.course_module import CourseBlock
@@ -833,19 +834,15 @@ class SplitModuleCourseTests(SplitModuleTest):
         assert root_block_key.block_id == 'course'
 
 
-class TestCourseStructureCache(SplitModuleTest):
+class TestCourseStructureCache(CacheIsolationMixin, SplitModuleTest):
     """Tests for the CourseStructureCache"""
 
+    # CacheIsolationMixin will reset the cache between test cases
+
+    # We'll use the "default" cache as a valid cache, and the "course_structure_cache" as a dummy cache
+    ENABLED_CACHES = ["default"]
+
     def setUp(self):
-        # use the default cache, since the `course_structure_cache`
-        # is a dummy cache during testing
-        self.cache = caches['default']
-
-        # make sure we clear the cache before every test...
-        self.cache.clear()
-        # ... and after
-        self.addCleanup(self.cache.clear)
-
         # make a new course:
         self.user = random.getrandbits(32)
         self.new_course = modulestore().create_course(
@@ -858,7 +855,8 @@ class TestCourseStructureCache(SplitModuleTest):
     def test_course_structure_cache(self, mock_get_cache):
         # force get_cache to return the default cache so we can test
         # its caching behavior
-        mock_get_cache.return_value = self.cache
+        enabled_cache = caches['default']
+        mock_get_cache.return_value = enabled_cache
 
         with check_mongo_calls(1):
             not_cached_structure = self._get_structure(self.new_course)
@@ -872,7 +870,7 @@ class TestCourseStructureCache(SplitModuleTest):
 
         # If data is corrupted, get it from mongo again.
         cache_key = self.new_course.id.version_guid
-        self.cache.set(cache_key, b"bad_data")
+        enabled_cache.set(cache_key, b"bad_data")
         with check_mongo_calls(1):
             not_corrupt_structure = self._get_structure(self.new_course)
 
diff --git a/common/lib/xmodule/xmodule/modulestore/tests/utils.py b/common/lib/xmodule/xmodule/modulestore/tests/utils.py
index 92dbbfd8e0..f59d7b6b75 100644
--- a/common/lib/xmodule/xmodule/modulestore/tests/utils.py
+++ b/common/lib/xmodule/xmodule/modulestore/tests/utils.py
@@ -1,14 +1,11 @@
 """
 Helper classes and methods for running modulestore tests without Django.
 """
-
-
 import os
 from contextlib import contextmanager
 from importlib import import_module
 from shutil import rmtree
 from tempfile import mkdtemp
-from unittest import TestCase
 from uuid import uuid4
 
 from contextlib2 import ExitStack
@@ -16,16 +13,15 @@ from path import Path as path
 
 from xmodule.contentstore.mongo import MongoContentStore
 from xmodule.modulestore.draft_and_published import ModuleStoreDraftAndPublished
-from xmodule.modulestore.edit_info import EditInfoMixin
 from xmodule.modulestore.inheritance import InheritanceMixin
 from xmodule.modulestore.mixed import MixedModuleStore
 from xmodule.modulestore.mongo.base import ModuleStoreEnum
 from xmodule.modulestore.mongo.draft import DraftModuleStore
 from xmodule.modulestore.split_mongo.split_draft import DraftVersioningModuleStore
+from xmodule.modulestore.tests.django_utils import ModuleStoreTestCase, TEST_DATA_ONLY_SPLIT_MODULESTORE_DRAFT_PREFERRED
 from xmodule.modulestore.tests.factories import ItemFactory
 from xmodule.modulestore.tests.mongo_connection import MONGO_HOST, MONGO_PORT_NUM
 from xmodule.modulestore.xml import XMLModuleStore
-from xmodule.modulestore.xml_importer import LocationMixin
 from xmodule.tests import DATA_DIR
 from xmodule.x_module import XModuleMixin
 
@@ -97,35 +93,16 @@ def remove_temp_files_from_list(file_list, dir):  # lint-amnesty, pylint: disabl
             os.remove(file_path)
 
 
-class MixedSplitTestCase(TestCase):
+class MixedSplitTestCase(ModuleStoreTestCase):
     """
-    Stripped-down version of ModuleStoreTestCase that can be used without Django
-    (i.e. for testing in common/lib/ ). Sets up MixedModuleStore and Split.
+    A minimal version of ModuleStoreTestCase for testing in common/lib/ that sets up MixedModuleStore and Split (only).
+
+    It also enables "draft preferred" mode, like Studio uses.
+
+    Draft/old mongo modulestore is not initialized.
     """
-    RENDER_TEMPLATE = lambda t_n, d, ctx=None, nsp='main': '{}: {}, {}'.format(t_n, repr(d), repr(ctx))
-    modulestore_options = {
-        'default_class': 'xmodule.hidden_module.HiddenDescriptor',
-        'fs_root': DATA_DIR,
-        'render_template': RENDER_TEMPLATE,
-        'xblock_mixins': (EditInfoMixin, InheritanceMixin, LocationMixin, XModuleMixin),
-    }
-    DOC_STORE_CONFIG = {
-        'host': MONGO_HOST,
-        'port': MONGO_PORT_NUM,
-        'db': f'test_mongo_libs_{os.getpid()}',
-        'collection': 'modulestore',
-        'asset_collection': 'assetstore',
-    }
-    MIXED_OPTIONS = {
-        'stores': [
-            {
-                'NAME': 'split',
-                'ENGINE': 'xmodule.modulestore.split_mongo.split_draft.DraftVersioningModuleStore',
-                'DOC_STORE_CONFIG': DOC_STORE_CONFIG,
-                'OPTIONS': modulestore_options
-            },
-        ]
-    }
+    CREATE_USER = False
+    MODULESTORE = TEST_DATA_ONLY_SPLIT_MODULESTORE_DRAFT_PREFERRED
 
     def setUp(self):
         """
@@ -134,15 +111,6 @@ class MixedSplitTestCase(TestCase):
         super().setUp()
         self.user_id = ModuleStoreEnum.UserID.test
 
-        self.store = MixedModuleStore(
-            None,
-            create_modulestore_instance=create_modulestore_instance,
-            mappings={},
-            **self.MIXED_OPTIONS
-        )
-        self.addCleanup(self.store.close_all_connections)
-        self.addCleanup(self.store._drop_database)  # pylint: disable=protected-access
-
     def make_block(self, category, parent_block, **kwargs):
         """
         Create a block of type `category` as a child of `parent_block`, in any
@@ -505,19 +473,3 @@ DOT_FILES_DICT = {
 TILDA_FILES_DICT = {
     "example.txt~": "RED"
 }
-
-
-class PureModulestoreTestCase(TestCase):
-    """
-    A TestCase designed to make testing Modulestore implementations without using Django
-    easier.
-    """
-
-    MODULESTORE = None
-
-    def setUp(self):
-        super().setUp()
-
-        builder = self.MODULESTORE.build()
-        self.assets, self.store = builder.__enter__()
-        self.addCleanup(builder.__exit__, None, None, None)
diff --git a/common/lib/xmodule/xmodule/tests/test_conditional.py b/common/lib/xmodule/xmodule/tests/test_conditional.py
index 696a022ffe..49c8603be3 100644
--- a/common/lib/xmodule/xmodule/tests/test_conditional.py
+++ b/common/lib/xmodule/xmodule/tests/test_conditional.py
@@ -4,6 +4,7 @@ import json
 import unittest
 from unittest.mock import Mock, patch
 
+from django.conf import settings
 from fs.memoryfs import MemoryFS
 from lxml import etree
 from opaque_keys.edx.keys import CourseKey
@@ -239,6 +240,7 @@ class ConditionalBlockXmlTest(unittest.TestCase):
         return courses[0]
 
     @patch('xmodule.x_module.descriptor_global_local_resource_url')
+    @patch.dict(settings.FEATURES, {'ENABLE_EDXNOTES': False})
     def test_conditional_module(self, _):
         """Make sure that conditional module works"""
 
diff --git a/common/lib/xmodule/xmodule/tests/test_course_module.py b/common/lib/xmodule/xmodule/tests/test_course_module.py
index f4c8dc8e49..b54d5291a1 100644
--- a/common/lib/xmodule/xmodule/tests/test_course_module.py
+++ b/common/lib/xmodule/xmodule/tests/test_course_module.py
@@ -432,6 +432,13 @@ class ProctoringProviderTestCase(unittest.TestCase):
         # since there are no validation errors or missing data
         assert self.proctoring_provider.from_json(default_provider) == default_provider
 
+    @override_settings(
+        PROCTORING_BACKENDS={
+            'DEFAULT': 'mock',
+            'mock': {},
+            'mock_proctoring_without_rules': {}
+        }
+    )
     def test_from_json_with_invalid_provider(self):
         """
         Test that an invalid provider (i.e. not one configured at the platform level)
@@ -451,7 +458,8 @@ class ProctoringProviderTestCase(unittest.TestCase):
         Test that a value with no provider will inherit the default provider
         from the platform defaults.
         """
-        default_provider = 'mock'
+        default_provider = settings.PROCTORING_BACKENDS.get('DEFAULT')
+        assert default_provider is not None
 
         assert self.proctoring_provider.from_json(None) == default_provider
 
diff --git a/common/lib/xmodule/xmodule/tests/test_services.py b/common/lib/xmodule/xmodule/tests/test_services.py
index c5b5373774..3e571756ca 100644
--- a/common/lib/xmodule/xmodule/tests/test_services.py
+++ b/common/lib/xmodule/xmodule/tests/test_services.py
@@ -59,15 +59,19 @@ class TestSettingsService(unittest.TestCase):
         with pytest.raises(ValueError):
             self.settings_service.get_settings_bucket(None)
 
+    @override_settings()
     def test_get_return_default_if_xblock_settings_is_missing(self):
         """ Test that returns default (or None if default not set) if XBLOCK_SETTINGS is not set """
-        assert not hasattr(settings, 'XBLOCK_SETTINGS')
+        # Per django docs, using override_settings() plus 'del' is how to test the absence of a setting:
+        del settings.XBLOCK_SETTINGS
         # precondition check
         assert self.settings_service.get_settings_bucket(self.xblock_mock, 'zzz') == 'zzz'
 
+    @override_settings()
     def test_get_return_empty_dictionary_if_xblock_settings_and_default_is_missing(self):
         """ Test that returns default (or None if default not set) if XBLOCK_SETTINGS is not set """
-        assert not hasattr(settings, 'XBLOCK_SETTINGS')
+        # Per django docs, using override_settings() plus 'del' is how to test the absence of a setting:
+        del settings.XBLOCK_SETTINGS
         # precondition check
         assert self.settings_service.get_settings_bucket(self.xblock_mock) == {}
 
diff --git a/lms/djangoapps/edxnotes/decorators.py b/lms/djangoapps/edxnotes/decorators.py
index ef039061b3..f92ca2939b 100644
--- a/lms/djangoapps/edxnotes/decorators.py
+++ b/lms/djangoapps/edxnotes/decorators.py
@@ -25,6 +25,9 @@ def edxnotes(cls):
             generate_uid, get_edxnotes_id_token, get_public_endpoint, get_token_url, is_feature_enabled
         )
 
+        if not settings.FEATURES.get("ENABLE_EDXNOTES"):
+            return original_get_html(self, *args, **kwargs)
+
         runtime = getattr(self, 'descriptor', self).runtime
         if not hasattr(runtime, 'modulestore'):
             return original_get_html(self, *args, **kwargs)
diff --git a/openedx/tests/completion_integration/test_services.py b/openedx/tests/completion_integration/test_services.py
index fd23895d5a..94fdf4e46b 100644
--- a/openedx/tests/completion_integration/test_services.py
+++ b/openedx/tests/completion_integration/test_services.py
@@ -188,7 +188,15 @@ class CompletionServiceTestCase(CompletionWaffleTestMixin, SharedModuleStoreTest
         ItemFactory.create(parent=library, category='problem', publish_item=False, user_id=self.user.id)
         ItemFactory.create(parent=library, category='problem', publish_item=False, user_id=self.user.id)
         ItemFactory.create(parent=library, category='problem', publish_item=False, user_id=self.user.id)
-        lib_vertical = ItemFactory.create(parent=self.sequence, category='vertical', publish_item=False)
+        # Create a new vertical to hold the library content block
+        # It is very important that we use parent_location=self.sequence.location (and not parent=self.sequence), since
+        # sequence is a class attribute and passing it by value will update its .children=[] which will then leak into
+        # other tests and cause errors if the children no longer exist.
+        lib_vertical = ItemFactory.create(
+            parent_location=self.sequence.location,
+            category='vertical',
+            publish_item=False,
+        )
         library_content_block = ItemFactory.create(
             parent=lib_vertical,
             category='library_content',
@@ -234,7 +242,11 @@ class CompletionServiceTestCase(CompletionWaffleTestMixin, SharedModuleStoreTest
         assert self.completion_service.vertical_is_complete(lib_vertical)
 
     def test_vertical_completion_with_nested_children(self):
-        parent_vertical = ItemFactory(parent=self.sequence, category='vertical')
+        # Create a new vertical.
+        # It is very important that we use parent_location=self.sequence.location (and not parent=self.sequence), since
+        # sequence is a class attribute and passing it by value will update its .children=[] which will then leak into
+        # other tests and cause errors if the children no longer exist.
+        parent_vertical = ItemFactory(parent_location=self.sequence.location, category='vertical')
         extra_vertical = ItemFactory(parent=parent_vertical, category='vertical')
         problem = ItemFactory(parent=extra_vertical, category='problem')
         parent_vertical = self.store.get_item(parent_vertical.location)
diff --git a/openedx/tests/settings.py b/openedx/tests/settings.py
deleted file mode 100644
index cdaa79ceb1..0000000000
--- a/openedx/tests/settings.py
+++ /dev/null
@@ -1,132 +0,0 @@
-"""
-Minimal Django settings for tests of common/lib.
-Required in Django 1.9+ due to imports of models in stock Django apps.
-"""
-import tempfile
-
-from django.utils.translation import ugettext_lazy as _
-
-ALL_LANGUAGES = []
-
-BLOCK_STRUCTURES_SETTINGS = dict(
-    COURSE_PUBLISH_TASK_DELAY=30,
-    TASK_DEFAULT_RETRY_DELAY=30,
-    TASK_MAX_RETRIES=5,
-)
-
-COURSE_KEY_PATTERN = r'(?P<course_key_string>[^/+]+(/|\+)[^/+]+(/|\+)[^/?]+)'
-COURSE_ID_PATTERN = COURSE_KEY_PATTERN.replace('course_key_string', 'course_id')
-USAGE_KEY_PATTERN = r'(?P<usage_key_string>(?:i4x://?[^/]+/[^/]+/[^/]+/[^@]+(?:@[^/]+)?)|(?:[^/]+))'
-
-
-COURSE_MODE_DEFAULTS = {
-    'bulk_sku': None,
-    'currency': 'usd',
-    'description': None,
-    'expiration_datetime': None,
-    'min_price': 0,
-    'name': 'Audit',
-    'sku': None,
-    'slug': 'audit',
-    'suggested_prices': '',
-}
-
-DATABASES = {
-    'default': {
-        'ENGINE': 'django.db.backends.sqlite3',
-        'NAME': 'default.db',
-        'USER': '',
-        'PASSWORD': '',
-        'HOST': '',
-        'PORT': '',
-    }
-}
-
-PROCTORING_BACKENDS = {
-    'DEFAULT': 'mock',
-    'mock': {},
-    'mock_proctoring_without_rules': {},
-}
-
-FEATURES = {}
-
-INSTALLED_APPS = (
-    'django.contrib.auth',
-    'django.contrib.contenttypes',
-    'django.contrib.sessions',
-    'django.contrib.sites',
-    'django_sites_extensions',
-    'lti_consumer',
-    'openedx.core.djangoapps.django_comment_common',
-    'openedx.core.djangoapps.discussions',
-    'openedx.core.djangoapps.video_config',
-    'openedx.core.djangoapps.video_pipeline',
-    'openedx.core.djangoapps.bookmarks.apps.BookmarksConfig',
-    'edxval',
-    'lms.djangoapps.courseware',
-    'lms.djangoapps.instructor_task',
-    'common.djangoapps.student',
-    'openedx.core.djangoapps.site_configuration',
-    'lms.djangoapps.grades.apps.GradesConfig',
-    'lms.djangoapps.certificates.apps.CertificatesConfig',
-    'openedx.core.djangoapps.user_api',
-    'common.djangoapps.course_modes.apps.CourseModesConfig',
-    'lms.djangoapps.verify_student.apps.VerifyStudentConfig',
-    'openedx.core.djangoapps.content_libraries',
-    'openedx.core.djangoapps.dark_lang',
-    'openedx.core.djangoapps.content.course_overviews.apps.CourseOverviewsConfig',
-    'openedx.core.djangoapps.content.block_structure.apps.BlockStructureConfig',
-    'openedx.core.djangoapps.catalog',
-    'openedx.core.djangoapps.self_paced',
-    'openedx.core.djangoapps.schedules.apps.SchedulesConfig',
-    'openedx.core.djangoapps.theming.apps.ThemingConfig',
-    'openedx.core.djangoapps.external_user_ids',
-    'openedx.core.djangoapps.demographics',
-    'openedx.core.djangoapps.agreements',
-
-    'lms.djangoapps.experiments',
-    'openedx.features.content_type_gating',
-    'openedx.features.course_duration_limits',
-    'openedx.features.discounts',
-    'milestones',
-    'celery_utils',
-    'waffle',
-    'edx_when',
-    'rest_framework_jwt',
-
-    # Django 1.11 demands to have imported models supported by installed apps.
-    'completion',
-    'common.djangoapps.entitlements',
-    'organizations',
-)
-
-LMS_ROOT_URL = "http://localhost:8000"
-
-MEDIA_ROOT = tempfile.mkdtemp()
-
-RECALCULATE_GRADES_ROUTING_KEY = 'edx.core.default'
-POLICY_CHANGE_GRADES_ROUTING_KEY = 'edx.core.default'
-POLICY_CHANGE_TASK_RATE_LIMIT = '300/h'
-
-
-SECRET_KEY = 'insecure-secret-key'
-SITE_ID = 1
-SITE_NAME = "localhost"
-PLATFORM_NAME = _('Your Platform Name Here')
-DEFAULT_FROM_EMAIL = 'registration@example.com'
-TRACK_MAX_EVENT = 50000
-USE_TZ = True
-
-RETIREMENT_SERVICE_WORKER_USERNAME = 'RETIREMENT_SERVICE_USER'
-RETIRED_USERNAME_PREFIX = 'retired__user_'
-
-PROCTORING_SETTINGS = {}
-
-ROOT_URLCONF = None
-RUN_BLOCKSTORE_TESTS = False
-
-# Software Secure request retry settings
-# Time in seconds before a retry of the task should be 60 mints.
-SOFTWARE_SECURE_REQUEST_RETRY_DELAY = 60 * 60
-# Maximum of 6 retries before giving up.
-SOFTWARE_SECURE_RETRY_MAX_ATTEMPTS = 6
diff --git a/pavelib/utils/test/suites/pytest_suite.py b/pavelib/utils/test/suites/pytest_suite.py
index 8d49f0cae7..40744ce513 100644
--- a/pavelib/utils/test/suites/pytest_suite.py
+++ b/pavelib/utils/test/suites/pytest_suite.py
@@ -308,10 +308,7 @@ class LibTestSuite(PytestSuite):
                 xdist_remote_processes = self.processes
             for ip in self.xdist_ip_addresses.split(','):
                 # Propogate necessary env vars to xdist containers
-                if 'pavelib/paver_tests' in self.test_id:
-                    django_env_var_cmd = "export DJANGO_SETTINGS_MODULE='lms.envs.test'"
-                else:
-                    django_env_var_cmd = "export DJANGO_SETTINGS_MODULE='openedx.tests.settings'"
+                django_env_var_cmd = "export DJANGO_SETTINGS_MODULE='lms.envs.test'"
 
                 env_var_cmd = '{} DISABLE_COURSEENROLLMENT_HISTORY={}' \
                     .format(django_env_var_cmd, self.disable_courseenrollment_history)