Sets up unit test environment.
Unlike Drupal\simpletest\WebTestBase::setUp(), UnitTestBase::setUp() does not install modules because tests are performed without accessing the database. Any required files must be explicitly included by the child class setUp() method.
Overrides UnitTestBase::setUp
public function setUp() {
// Initiate the generator. This will lazy-load uuid.inc.
$this->uuid = new Uuid();
parent::setUp();
}