Note to myself: If I ever see that error again when running PHPUnit tests
Invalid argument supplied for foreach() phar://C:/Program Files (x86)/PHPUnit/phpunit.phar/PHPUnit/Framework/Constraint/TraversableContains.php:110 phar://C:/Program Files (x86)/PHPUnit/phpunit.phar/PHPUnit/Framework/Constraint.php:82 phar://C:/Program Files (x86)/PHPUnit/phpunit.phar/PHPUnit/Framework/Constraint/And.php:113
please remember that $this->contains() is not the same as $this->stringContains(). The first one is a constraint for arrays, the second one is for strings.