I'd use this instead.
```php
if (defined('JSON_C_VERSION') && PHP_INT_SIZE > 4) {
	$expected = 9223372036854775807;
} elseif (defined('JSON_C_VERSION') {
	$expected = '9223372036854775807';
} else {
	$expected = '12345678901234567890';
}
Assert::same( array($expected), Json::decode('[12345678901234567890]') ); 
```