Default-flow is never stored on exclusive gateway:
* Setting the sequence flows coming out from exclusive gateway, then setting the default flow does not set in xml definition any element/attribute corresponding to default flow.
* Setting default-flow never changes the xml.
Designer version: 5.11.2
*** Default flow does work on service tasks ***
No special test unit required. Add ex.gateway, set default flow - it simply never gets stored, nothing happens in xml.