assertNotNull("Validation should return a boolean result for: " + cron, Boolean.valueOf(result));
        }
    }

    // Test edge cases to understand the validation behavior
    public void test_edgeCaseBehavior() {
        String[] edgeCases = { "0 0 25 * * ?", // Invalid day of month
                "0 60 * * * ?", // Invalid minute
                "0 0 0 32 1 ?", // Invalid day
                "0 0 0 1 13 ?", // Invalid month