added testing

CONTRIBUTING.md

@@ -21,3 +21,12 @@ When working on the tool, use this to link your command for development:
 ```sh
 npm link
 ```
+
+## Testing Your Changes
+
+- This tool uses a framework called Jest for testing.
+- To write additional tests, look for files ending in `.test.js` and find the `describe()` suite that matches the task you want to test.
+- When creating a new test or test suite, please add to the `describe()` or `test()` method what the purpose of the test is.
+- To run all the test suites, type `npm run test` in the command line.
+- To exclude a test, you may go into the test file and change `test()` to `test.skip()` to exclude a single test.
+- To exclude all tests/suites except one, add the `only()` method to `describe()` or `it()` to run that test suite or individual test.