function test_addCopies()
{
$title = "Three Blind Mice";
$test_book = new Book($title);
$test_book->save();
$test_copy = new Copy($amount = 1, $test_book->getId());
$test_copy->save();
$title2 = "Dune";
$test_book2 = new Book($title2);
$test_book2->save();
$test_copy->addCopies(1);
$result = $test_copy->getAmount();
$this->assertEquals(2, $result);
}
