Reset PHPUnit testcase properties to save memory after each test.

BaseTestCase.php

<?php

abstract class BaseTestCase extends PHPUnit\Framework\TestCase
{
    /**
     * Reset the properties to save memory after each test.
     * @see https://kriswallsmith.net/post/18029585104/faster-phpunit
     */
    protected function tearDown(): void
    {
        (function () {
            foreach ((new \ReflectionObject($this))->getProperties() as $prop) {
                if ($prop->isStatic() || strpos($prop->getDeclaringClass()->getName(), 'PHPUnit\\') === 0) {
                    continue;
                }

                unset($this->{$prop->getName()});
            }
        })->call($this);
    }
}