Add instructions for running tests locally to README.md

- Added detailed steps for running tests and checking test coverage using `pytest` and `coverage`.
- Positioned the new instructions under the "Testing" subsection within the "Contributing" section.

This update provides clear guidance for contributors to verify the functionality of the CLI tool on their local machines.

README.md

@@ -392,6 +392,25 @@ To update the project, run the following command:
 pip install pieces-cli --upgrade
 ```
 
+
+### Testing
+To discover and run all the test cases in the repository, run the following command:
+
+```shell
+pytest
+```
+
+To check the test coverage, you can use the coverage package. Install coverage with:
+```shell
+pip install coverage
+```
+
+Run the tests with coverage using the following command:
+```shell
+coverage run -m pytest
+coverage report
+```
+
 ### Uninstallation
 To uninstall the project, run the following command: