Run all tests in development.md (#2951)

This PR changes the directions in development.md to run all tests.

Note that I opted to explicitly specify `test_*.py` instead of doing test discovery so it's obvious that you can also specify specific files.

Development.md

@@ -84,10 +84,11 @@ make help
  ```
 
 ### 8. Testing
+To run tests, refer to the following:
 #### Unit tests
 
 ```bash
-poetry run pytest ./tests/unit/test_sandbox.py
+poetry run pytest ./tests/unit/test_*.py
 ```
 
 #### Integration tests