On the JetBrains blog Gary Hockin explains how to easily run a single PHPUnit test.

To run all the tests in a single file, right-click the test in the Project Pane (the left-hand navigation pane), and select Run . To run all the tests in a single class, right-click the class name in the editor, and select Run . To run the tests in a single method, right-click the method name, and select Run .

https://blog.jetbrains.com/phpstorm/2017/01/working-with-phpunit-and-phpstorm/