// Should not add any language fields
        assertNull(doc.get("lang"));
        assertEquals(0, doc.size());
    }

    @Test
    public void test_updateDocument_skipExistingLangFields() {
        Map<String, Object> doc = new HashMap<>();
        doc.put("lang", "ja");
        doc.put("title", "タイトル");
        doc.put("title_ja", "既存のタイトル"); // Should not be overwritten

Shinsuke Sugaya <******@****.***> 1773442886 +0900