public function testRetainAllElements() { $collectionA = new BasicCollection(); $collectionA->add('foo'); $collectionA->add('bar'); $collectionB = new BasicCollection(); $collectionB->add('foo'); self::assertTrue($collectionA->retainAll($collectionB)); self::assertFalse($collectionA->retainAll($collectionB)); $elements = $collectionA->toArray(); self::assertEquals('foo', $elements[0]); }