Cannot run PHPUnit

[mattdillon100]

Installed CoasterCMS via composer today so it is the latest version.

PHPUnit is v6.5.6

Running phpunit results in the following error:

Warning: is_dir() expects parameter 1 to be a valid path, object given in /home/matt/.config/composer/vendor/phpunit/phpunit/src/Runner/BaseTestRunner.php on line 56

Catchable fatal error: Object of class PHPUnit\Framework\TestSuite could not be converted to string in /home/matt/.config/composer/vendor/phpunit/phpunit/src/Runner/StandardTestSuiteLoader.php on line 32

I have ran composer install and composer dump-autoload