if (readingObj instanceof List) {
                @SuppressWarnings("unchecked")
                final List<String> existingValues = (List<String>) readingObj;
                concatValues(existingValues, readings[i]);
                map.put(FieldNames.READING_PREFIX + i, existingValues.stream().distinct().toList());
            } else {

        assertTrue(tags.contains("existing"));
    }

    @Test
    public void testConcatValues() {
        // Test static concatValues method
        List<String> dest = new java.util.ArrayList<>();
        dest.add("existing");

        SuggestItem.concatValues(dest, "new1", "new2", "existing");

        assertEquals(3, dest.size());
        assertTrue(dest.contains("existing"));

     * @param dest The destination list.
     * @param newValues The new values to add.
     * @param <T> The type of the values.
     */
    protected static <T> void concatValues(final List<T> dest, final T... newValues) {
        for (final T value : newValues) {
            if (!dest.contains(value)) {
                dest.add(value);
            }
        }
    }

    /**