}
    }

    // Test edge cases to understand the validation behavior
    public void test_edgeCaseBehavior() {
        String[] edgeCases = { "0 0 25 * * ?", // Invalid day of month
                "0 60 * * * ?", // Invalid minute
                "0 0 0 32 1 ?", // Invalid day
                "0 0 0 1 13 ?", // Invalid month
        };

        assertFalse(thumbnailGenerator.generate("", tempOutputFile));
    }

    public void test_generate_withNullOutputFile() {
        // Test generation with null output file
        String thumbnailId = "test-thumbnail-002";
        assertFalse(thumbnailGenerator.generate(thumbnailId, null));
    }

    public void test_generate_withInvalidOutputPath() throws IOException {
        // Test generation with non-writable output file

                "config_id", "W01", //
                "url", "http://test.com/001"//
        )));
        docList.add(new HashMap<>(Map.of(//
                "_id", "002", //
                "thumbnail", "http://test.com/002", //
                "url", "http://test.com/002"//
        )));
        indexingHelper.sendDocuments(client, docList);
        assertEquals(0, docList.size());
        assertEquals(2, sentDocList.size());

    if (c <= '\u001f' || c >= '\u007f') {
      return true
    }
    // Check for the characters mentioned in the WHATWG Host parsing spec:
    // U+0000, U+0009, U+000A, U+000D, U+0020, "#", "%", "/", ":", "?", "@", "[", "\", and "]"
    // (excluding the characters covered above).
    if (" #%/:?@[\\]".indexOf(c) != -1) {
      return true
    }
  }
  return false
}