Update unit testing documentation

tests/unit/README.md

@@ -1,9 +1,17 @@
 # Llama Stack Unit Tests
 
+## Unit Tests
+
+Unit tests verify individual components and functions in isolation. They are fast, reliable, and don't require external services.
+
+### Prerequisites
+
+1. **Python Environment**: Ensure you have Python 3.12+ installed
+2. **uv Package Manager**: Install `uv` if not already installed
+
 You can run the unit tests by running:
 
 ```bash
-source .venv/bin/activate
 ./scripts/unit-tests.sh [PYTEST_ARGS]
 ```
 
@@ -19,3 +27,21 @@ If you'd like to run for a non-default version of Python (currently 3.12), pass
 source .venv/bin/activate
 PYTHON_VERSION=3.13 ./scripts/unit-tests.sh
 ```
+
+### Test Configuration
+
+- **Test Discovery**: Tests are automatically discovered in the `tests/unit/` directory
+- **Async Support**: Tests use `--asyncio-mode=auto` for automatic async test handling
+- **Coverage**: Tests generate coverage reports in `htmlcov/` directory
+- **Python Version**: Defaults to Python 3.12, but can be overridden with `PYTHON_VERSION` environment variable
+
+### Coverage Reports
+
+After running tests, you can view coverage reports:
+
+```bash
+# Open HTML coverage report in browser
+open htmlcov/index.html  # macOS
+xdg-open htmlcov/index.html  # Linux
+start htmlcov/index.html  # Windows
+```