Configuration for phpunit is in the ./phpunit.xml file.

If you haven't already done so, you can setup unit tests in PHPStorm. To do so, first go to File > Settings > Languages & Frameworks > PHP > Test Frameworks and add new PHPUnit Local configuration. Select Use composer autoloader and in the field below navigate to your Magento installation folder and select /vendor/autoload.php file.

Go to Run > Edit configuration menu and add new PHPUnit configuration. For Test Runner options select Defined in configuration file and add specific phpunit configuration file path to the ./phpunit.xml file in module's root directory.

Create new file ./Test/autoload.php by copying the file ./Test/autoload-sample.php. In the newly created file change path to the magento's root folder, for example /var/www/html/magento/app/bootstrap.php.

Now test configuration is set and you can run tests by activating run command from the top right toolbar.

All tests must pass.

Note: Tests will fail if you already have installed the module in Magento, because Magento will load both your local module and the module from Magento. In such a configuration, you need to rename the module folder in Magento, run tests, and rename it back.