You can feel and hear a healthy sprag from a damaged one pretty easily by turning the driveshaft with your hands but if possible it's certainly a good idea to pull the trans.
This method will certainly bite you in the a$$. Eventually.
There are a few failure modes - bad springs and rollers are one.
Driving it around, functioning and seeming to be okay is not a valid test.
Having half the springs smashed will certainly change how it feels when spinning the output shaft. But I'm not going to trust that one either. Take it out and look at it, or roll the dice.
