Add info about test suite to README

README.md

@@ -23,5 +23,13 @@ uv run fastapi dev src/allmende_payment_system/app.py
 ```
 A demo user will be created automatically.
 
+### Testing
+
+APS uses pytest. You can run the test suite with:
+
+```bash
+uv run pytest
+```
+
 ## License
 This project is licensed under the [European Union Public Licence (EUPL)](https://joinup.ec.europa.eu/collection/eupl).