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"));