public static DynamicVoters parse(String input) {
        input = input.trim();
        List<DynamicVoter> voters = new ArrayList<>();
        for (String voterString : input.split(",")) {
            if (!voterString.isEmpty()) {
                voters.add(DynamicVoter.parse(voterString));
            }
        }
        return new DynamicVoters(voters);
    }
@Test
    public void testParsingEmptyStringFails() {
        assertEquals("No voters given.",
            assertThrows(IllegalArgumentException.class,
                () -> DynamicVoters.parse("")).
                    getMessage());
    }