Setting an invalid (not supported) resolution with Morena 7 seemingly succeeds, and afterwards the driver even reports this incorrect value as actual setting, but it does not work. However, beforehand, you can query the supported resolutions.

Interestingly my consumer-grade HP LaserJet is presented as HP LJ M139M142 (NET) but it shows up also as a "generic" WSD (Web Services for Devices) Scan Device. But the latter reports incorrect resolutions (75, 150, 300) whereas the HP LJ one reports the correct values 200, 300, 600.