private static List<String> convert(final List<TextParam> values) {
        final List<String> result = new ArrayList<>();
        for (TextParam tp : values) {
            result.add(tp.toString());
        }
        return result;
    }
This can, of course, only test the non-ui-parts of the {@link TextSpinner}
main/src/test/java/cgeo/geocaching/ui/TextSpinnerTest.java