public function testRemoveAllElements()
 {
     $collectionA = new BasicCollection();
     $collectionA->add('foo');
     $collectionA->add('bar');
     $collectionB = new BasicCollection();
     $collectionB->add('foo');
     $collectionB->add('foo');
     $collectionB->add('baz');
     self::assertTrue($collectionA->removeAll($collectionB));
     self::assertEquals(1, $collectionA->size());
     self::assertFalse($collectionB->removeAll($collectionA));
 }