Add unit tests for handlers

**Description**
Currently handlers lacks proper monitoring support.

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

**Priority**: Low/Medium

The issue names no files, handlers, or test entry points. Start by locating the handlers implementation and any existing monitoring or unit-test conventions; clarify the configuration surface and sensible defaults before coding. Done means handlers have configurable monitoring, defaults are covered, and the unit tests pass.

Written by the indexing model from the issue text.