How to test a MOV with no visible damage
A MOV can be tested with a small applied current (such as 1mA) and that voltage compared with the datasheet specification. 

For example, a Bourns MOV-07D221K should drop 198V minimum, 220V nominal 242V maximum at 1mA. That test should be done quickly with appropriate equipment to limit the current to avoid heating the MOV too much, particularly with higher voltage MOVs. Obviously, you would do that out of circuit. 

Chances are if the MOV looks okay (and tests open circuit) it is, they normally fail shorted and only go open when they are blown open by excessive current (which tends to be detectable visually or by odor).