I have to ask you if you feel testing a nicad by voltage reading without a load is the same as with a load. Try this: let your battery drain down until the last green light is lite. Then put a 20 OHM resister across the red and black lead while the tester is still connected. Caution: we are talking the receiver battery only 4.8V nom. It is apt to draw it right down into the red. Load makes a huge difference.
You can check other sources but to me checking the battery with a sizable load is more important than all the electronic charging / cycling gear on the market. They are not foolproof! If you use this type of gear you darn well better be checking before the first flight.
Ace