Jetpack includes several unit tests that you can run in your local environment before you submit a new Pull Request.

To get started, you can follow the instructions here to install PHPUnit on your machine.

You'll also need to install a mySQL server, to run the tests.

We've included two styles to run unit tests here, depending on whichever you feel most comfortable with. Whichever you choose, the end result will be the same.

Option #1: putting everything inside the Jetpack repo you've already cloned. This option is probably the best option if you already cloned the repo and you just want to test that your changes didn't break anything.

Option #2: clone the repo inside a WordPress svn checkout. This option is the simplest. It's the best if you don't already have any work in progress or are just starting out.

The easiest way to get up and running is to download trunk, of WordPress:

svn checkout http://develop.svn.wordpress.org/trunk wordpress-tests

This will checkout the codebase into the folder wordpress-tests in the root of the repo.

You'll need to copy wp-tests-config-sample.php to wp-tests-config.php and update the credentials to point to an existing database. This database will be wiped clean every time you run phpunit, so don't use a production database or any database whose content you might care about.

Before running tests, we'll need to tell PHPUnit where the bootstrapping code lives:

export WP_DEVELOP_DIR=wordpress-tests/tests/phpunit

To run tests on your machine, you can run phpunit while in the Jetpack directory.

If you're not familiar with PHP Unit Testing, you can also check this tutorial

Simply checkout Jetpack as a plugin into the wp-content/plugins directory

Run phpunit while in the Jetpack directory.