Using ramsey/uuid 4.7.5, class existence fails at https://github.com/flow-php/flow/blob/1.x/src/core/etl/src/Flow/ETL/Row/Entry/Type/Uuid.php#L26 because of interface deprecation.
And because of concrete class implementation at the next line and unit test checks on concrete class, it would be smarter to check on concrete class rather than its interface.