Dodge Repair: No brakes on right front (and likely left rear)

Question
1998 dodge durango 5.2 v8 4x4 has no pressure, front passenger not working, no fluid leak..whats wrong

Answer
Hi Crissy,
In the absence of pressure on half the system and with absolutely no fluid leak, I would suspect a master cylinder malfunction as the reason. The master cylinder has 2 pistons (right front/left rear, left front/right rear) so one half of the master cylinder has gone bad. But nonetheless
do the following:
With engine running, apply brake very slowly. Gradually increase the pedal effort while watching brake warning light. Increase to very high effort, hold it for 30 seconds.
Tell me either: warning light comes on with moderate pressure on the pedal and stays on when pedal is released OR warning light comes on with moderate to heavy pressure but goes out when pedal is released OR warning light comes on only with heavy pressure for several seconds and pedal moves down with continuing heavy pressure OR warning light doesn't come on.
Please let me know how this test works out. I suspect that replacing the master cylinder will solve this problem.
Please read the PS (below) and respond to it.
Thanks,
Roland