public function testAppend()
 {
     $arrayObject = new ArrayObject([1, 2, 3]);
     $new = $arrayObject->append(4);
     $this->assertNotSame($new, $arrayObject);
     $this->assertSame([1, 2, 3, 4], $new->getArrayCopy());
 }
 /**
  * @param string $arg
  */
 public function appendArg($arg)
 {
     Assertion::string($arg);
     $this->args = $this->args->append($arg);
 }