update README; enhance installation instructions and add test execution guidelines

Author: dcloud347

README.md

@@ -26,9 +26,16 @@ Give an frontier agent a reliable tool to visually verify its code changes in a
 
 ```bash
 pip install -e .
-pip install -e ".[dev]"      # includes pytest, ruff
+pip install -e ".[dev]"      # includes pytest, pytest-mock, ruff
 playwright install chromium  # required for WebAgent
 ```
+### Run tests
+
+```bash
+pytest                  # run all tests
+pytest -v               # verbose output
+pytest -k test_name     # run a single test by name
+```
 
 ### Configure