ValidationContext vctx = new ValidationContext();
vctx.add(new Check("string", new MinLengthConstraint(2)));
Vtor vtor = new Vtor();
vtor.validate(vctx, new Foo());
assertTrue(vtor.hasViolations());
List<Violation> vlist = vtor.getViolations();
assertFalse(vlist.isEmpty());
assertEquals(1, vlist.size());