Fixed issues with TracDBCreateDatabaseMixin

- The mixin is now compatible with TestCase.setUpTestData
- The mixin now has teardown logic and can be used more than
  once in the testsuite

tracdb/testutils.py

@@ -67,6 +67,17 @@ def create_db_tables_for_unmanaged_models(schema_editor):
         _create_db_table_for_model(model, schema_editor)
 
 
+def destroy_db_tables_for_unmanaged_models(schema_editor):
+    """
+    Destroy tables for all unmanaged models in the tracdb app
+    """
+    appconfig = apps.get_app_config("tracdb")
+    for model in appconfig.get_models():
+        if model._meta.managed:
+            continue
+        schema_editor.delete_model(model)
+
+
 class TracDBCreateDatabaseMixin:
     """
     A TestCase mixin that creates test tables for all the tracdb apps.
@@ -75,6 +86,12 @@ class TracDBCreateDatabaseMixin:
 
     @classmethod
     def setUpClass(cls):
-        super().setUpClass()
         with connections["trac"].schema_editor() as schema_editor:
             create_db_tables_for_unmanaged_models(schema_editor)
+        super().setUpClass()
+
+    @classmethod
+    def tearDownClass(cls):
+        super().tearDownClass()
+        with connections["trac"].schema_editor() as schema_editor:
+            destroy_db_tables_for_unmanaged_models(schema_editor)