# Task 7: Update Timer to Use HubEntity - Report

## Status: DONE

## Summary

Updated `Timer` class to inherit from `HubEntity` instead of being a standalone class.

## Changes Made

### `aiopulse/timer.py`
- Changed `Timer` to inherit from `HubEntity` (was standalone)
- Added proper type annotations
- Removed redundant `hub` and `id` assignments (now from `HubEntity`)
- Added `from __future__ import annotations` for modern type hints
- Fixed `__str__` to handle `None` days gracefully

### `tests/test_timer.py`
- Updated to use `MagicMock` for hub (simpler test setup)
- Added tests for `CallbackMixin` integration (`callback_subscribe`, `callback_unsubscribe`, `notify_callback`)
- Tests verify Timer now has `_update_callbacks` attribute from `HubEntity`/`CallbackMixin`

## TDD Process

1. **RED**: Wrote 7 tests first - 6 failed (no `_update_callbacks`, no callback methods, `__str__` crash on None days)
2. **GREEN**: Implemented `Timer(HubEntity)` - tests passed
3. **REFACTOR**: None needed - implementation was minimal

## Test Results

```
tests/test_timer.py - 7 passed
Full suite - 182 passed
```

## Commit

- `9fdea77` - refactor: Timer inherits from HubEntity
