Magento’s documentation tells you to run tests with the following
php bin/magento dev:tests:run unit
This isn’t wrong, but it pretty time consuming. You’re running every test in the suite. This one liner will let you run an individual test
vendor/bin/phpunit -c dev/tests/unit/phpunit.xml.dist path/to/Test/Unit/SomeTest.php
Thanks to Vinai Kopp for the reminder, and don’t forget to checkout his Mage 2 Katas series on youtube.