public function testAddAllYieldsUnion()
 {
     $setA = new BasicSet(new SimpleComparator());
     $setA->add('foo');
     $setA->add('bar');
     $setB = new BasicSet(new SimpleComparator());
     $setB->add('foo');
     $setB->add('baz');
     $setA->addAll($setB);
     self::assertTrue($setA->containsAll($setB));
 }