assertEquals("ja", doc.get("lang"));
        assertEquals("タイトル", doc.get("title_ja"));
        assertEquals("コンテンツ", doc.get("content_ja"));
    }

    @Test
    public void test_updateDocument_noLanguageDetected() {
        Map<String, Object> doc = new HashMap<>();
        doc.put("title", "xyz");
        doc.put("content", "xyz");

        // Without a real detector, this will throw NullPointerException