make DatabaseCreation._destroy_test_db() clear the test database

django_mongodb/creation.py

@@ -1,3 +1,4 @@
+from django.conf import settings
 from django.db.backends.base.creation import BaseDatabaseCreation
 
 
@@ -7,6 +8,11 @@ def _execute_create_test_db(self, cursor, parameters, keepdb=False):
             self._destroy_test_db(parameters["dbname"], verbosity=0)
 
     def _destroy_test_db(self, test_database_name, verbosity):
+        # At this point, settings still points to the non-test database. For
+        # MongoDB, it must use the test database.
+        settings.DATABASES[self.connection.alias]["NAME"] = test_database_name
+        self.connection.settings_dict["NAME"] = test_database_name
+
         for collection in self.connection.introspection.table_names():
             if not collection.startswith("system."):
                 self.connection.database.drop_collection(collection)