Add unit tests for models

**Description**
Currently middleware lacks proper notifications support.

**Proposed solution**
Add configurable notifications with sensible defaults.

**Priority**: Low/Medium

The title asks for unit tests for models, while the description asks for configurable middleware notifications, so first reconcile the intended scope with the issue author. No files, test paths, or entry points are named; identify the relevant middleware and model code before defining tests and a clear completion criterion.

Written by the indexing model from the issue text.