* @return A List of strings, never null
     * @throws IllegalArgumentException if the value is not a String or List
     */
    @SuppressWarnings("unchecked")
    public static List<String> getStringList(final Map<String, Object> map, final String key) {
        final Object value = map.get(key);
        if (value == null) {
            return new ArrayList<>();
        }

        map.put("empty", Arrays.asList());

        List<String> result = MapValueExtractor.getStringList(map, "list");
        assertEquals(3, result.size());
        assertEquals("a", result.get(0));
        assertEquals("b", result.get(1));
        assertEquals("c", result.get(2));

        List<String> empty = MapValueExtractor.getStringList(map, "empty");
        assertTrue(empty.isEmpty());