Automatically unset all properties with PHPUnit.

UnitTestCase.php

<?php

use PHPUnit\Framework\TestCase;

/**
 * Base class for all unit tests.
 */
abstract class UnitTestCase extends TestCase
{
    /**
     * @inheritdoc
     */
    protected function tearDown()
    {
        $reflection = new \ReflectionObject($this);
        foreach ($reflection->getProperties() as $property) {
            if ($property->isStatic()) {
                continue;
            }

            if (strpos($property->getDeclaringClass()->getName(), 'PHPUnit_') !== 0) {
                $property->setAccessible(true);
                $property->setValue($this, null);
            }
        }
    }
}