* @param analyzer The analyzer to use for analyzing field values.
     * @return A list of suggest items extracted from the document.
     */
    List<SuggestItem> parseDocument(Map<String, Object> document, String[] fields, String[] tagFieldNames, String roleFieldName,
            String langFieldName, ReadingConverter readingConverter, ReadingConverter contentsReadingConverter, Normalizer normalizer,

    // ============================================================
    // Tests for parseDocument edge cases
    // ============================================================

    @Test
    public void test_parseDocument_emptyDocument() throws Exception {
        Map<String, Object> document = new HashMap<>();

        List<SuggestItem> items = parser.parseDocument(document, supportedFields, tagFieldNames, roleFieldName, "lang",

            throw new SuggesterException("Failed to create SuggestItem from query log.", e);
        }

        return items;
    }

    @Override
    public List<SuggestItem> parseDocument(final Map<String, Object> document, final String[] fields, final String[] tagFieldNames,
            final String roleFieldName, final String langFieldName, final ReadingConverter readingConverter,

            }
            final SuggestItem[] items = stream.flatMap(document -> {
                try {
                    return contentsParser
                            .parseDocument(document, ctx.getSupportedFields(), ctx.getTagFieldNames(), ctx.getRoleFieldName(),
                                    ctx.getLangFieldName(), readingConverter, contentsReadingConverter, normalizer, analyzer)

        document.put("title", "タイトル");

        SuggestAnalyzer analyzer = suggester.settings().analyzer().new DefaultContentsAnalyzer();
        List<SuggestItem> items = defaultContentsParser.parseDocument(document, supportedFields, tagFieldNames, roleFieldName, "lang",
                createDefaultReadingConverter(), createDefaultReadingConverter(), createDefaultNormalizer(), analyzer);

        assertNotNull(items);