When talking of testing extended range of a cruise missile, you are essentially talking of testing a plane for extended range.
Now doing a captive trial for extended range is what you would not want in the first place. A loop trial is fine, but that too would not mean a proper validation trial for range.
Now going by NOTAM and NAVREA, it was not tested for an extended range in first place. Also the reports indicates that it is more about testing subsystems rather then range. So the test was a regular missile picked from assembly line rather then a newly developed ER one.
@Immanuel As per popular believe, it is not an easy job to upgrade the already deployed systems. The cannisterisation of the missile prevents it from being FUP. A whole team of engineers would be required at site to carry out even a minor EEPROM replacement activity. The logical way ahead is to go for upgraded missile replacement gradually in norms of mid life upgrade. New system would replace the old ones in the field and old system would be brought back to assembly line for upgrades.
But first, a couple of validation trials would be needed for range extension.