In examples 5.1.2.1. of the spec (§5.1.2. Methods for validating method and constructor constraints) it says "Do we need more examples?". The answer is yes ;o)

Method validation is new so it would make things clearer to have more examples. I've been playing with this new feature [1] and I have some doubts on the way I am using validateReturnValue (check [2]).

So I think a more concrete and complete example in the spec would help. You can have a look at my GitHub [1] and the experiments I've been playing with.

[1] https://github.com/agoncal/agoncal-sample-bean-validation
[2] https://github.com/agoncal/agoncal-sample-bean-validation/blob/master/01-Method/src/test/java/org/agoncal/sample/beanvalidation/method/CardValidatorTest.java