words.add("banana");
        words.add("cherry");

        PopularWordsResponse response = new PopularWordsResponse("test-index", 100, words, 10, new ArrayList<>());

        assertNotNull(response.getWords());
        assertEquals(3, response.getWords().size());
        assertTrue(response.getWords().contains("apple"));
        assertTrue(response.getWords().contains("banana"));

  }

  @Override
  protected Map<String, Map<Integer, Character>> makePopulatedMap() {
    Table<String, Integer, String> table = HashBasedTable.create();
    table.put("foo", 1, "apple");
    table.put("bar", 1, "banana");
    table.put("foo", 3, "cat");
    return transformValues(table, TableCollectionTest.FIRST_CHARACTER).rowMap();
  }

    }

    @Test
    @DisplayName("Should join with multi-character delimiter")
    void testJoinWithMultiCharDelimiter() {
        String result = StringUtil.join(" - ", "apple", "banana", "cherry");
        assertEquals("apple - banana - cherry", result);
    }

    @Test
    @DisplayName("Should handle null delimiter by inserting 'null' string")
    void testJoinWithNullDelimiter() {