Phpunit error in PhpStorm

Silly mistake on my part... simply forgot to add phpunit as a dependency in the project. For anyone else that gets this error, to composer.json add:

"require-dev": {
    "phpunit/phpunit": "3.7.*"
},

And then run:

composer update

That solved the problem.

I had the same issue with Ubuntu 16.10, phpStorm 2017.2 and Laravel 5.5

Fixed it by uninstalling phpunit from my Ubuntu-system with

sudo apt-get remove phpunit
sudo apt-get install --autoremove

or for mac:

brew uninstall phpunit
brew install phpunit

My PhpStorm configuration (File -> Settings -> Languages & Frameworks -> PHP -> Test Frameworks):

Works great, now!

In my case the problem was caused by following set of reasons:

1. I installed phpunit using composer with composer require phpunit/phpunit command. I did not pay attention that by default it used php7 and it installed phpunit6 which has class names with namespaces (PHPUnit\TextUI\ResultPrinter).
2. IDE runs old version of phpunit which expects class names without namespaces (PHPUnit_TextUI_ResultPrinter)

I decided to reinstall phpunit running same composer command as above, but under php 5.6 (because it was important to be compatible with php5.6) and it installed phpunit 5.7 . But it is possible to go with newer version of phpunit and php: Settings > PHP > PHPUnit :: "Use composer autoloader" (set path to phpunit executable inside vendors (it was vendors/bin/phpunit in my case))