}
        assertTrue(lookupMessage(unknownCode).isEmpty());
    }

    @Test
    @DisplayName("Codes: all non-negative and unique")
    void codes_are_non_negative_and_unique() {
        // Edge checks: ensure there are no negative or duplicate codes
        Set<Integer> seen = new HashSet<>();
        for (int c : WinError.WINERR_CODES) {