Add coverage report details

Author: simonkurtz-MSFT

tests/README.md

@@ -88,10 +88,16 @@ Both scripts:
 
 #### Viewing Coverage Reports
 
-**In VS Code:**
-- Coverage is automatically displayed in the file explorer (showing % next to Python files)
-- Coverage gutters appear in open Python files (green/red/orange lines)
-- Install the "Coverage Gutters" extension for enhanced visualization
+**In VS Code (no extra extensions):**
+- Open the Testing view (beaker icon in the Activity Bar).
+- Click the "Toggle Code Coverage" shield button in the Testing toolbar.
+- Run tests from the Testing view (Run All or individual test runs).
+- The Explorer will decorate Python files with coverage percentages, and the editor will show covered/uncovered lines.
+- Make sure the Python extension is enabled and `coverage`/`pytest-cov` are available in your venv. If needed:
+   ```powershell
+   pip install coverage pytest-cov
+   ```
+- Note: Running pytest only from the terminal won’t decorate the Explorer. Use the Testing UI to see coverage overlays.
 
 **In Browser:**
 - Open `htmlcov/index.html` in your browser for detailed coverage information