Add Chinese variant fallback tests

Co-authored-by: pierotofy <1951843+pierotofy@users.noreply.github.com>

libretranslate/tests/test_api/test_language_variant_fallback.py

@@ -29,6 +29,30 @@ def client_with_pt(app_with_pt):
     return app_with_pt.test_client()
 
 
+@pytest.fixture()
+def app_with_zh():
+    sys.argv = ['', '--load-only', 'en,zh']
+    app = create_app(get_args())
+    yield app
+
+
+@pytest.fixture()
+def client_with_zh(app_with_zh):
+    return app_with_zh.test_client()
+
+
+@pytest.fixture()
+def app_with_zt():
+    sys.argv = ['', '--load-only', 'en,zt']
+    app = create_app(get_args())
+    yield app
+
+
+@pytest.fixture()
+def client_with_zt(app_with_zt):
+    return app_with_zt.test_client()
+
+
 def test_auto_detect_fallback_pt_to_pb(client_with_pb):
     response = client_with_pb.post("/translate", data={
         "q": "Olá mundo",
@@ -69,3 +93,31 @@ def test_explicit_language_no_fallback(client_with_pb):
     assert response.status_code == 400
     assert "error" in response_json
 
+
+def test_auto_detect_fallback_zt_to_zh(client_with_zh):
+    response = client_with_zh.post("/translate", data={
+        "q": "你好世界",
+        "source": "auto",
+        "target": "en",
+        "format": "text"
+    })
+    
+    response_json = json.loads(response.data)
+    assert response.status_code == 200
+    assert "translatedText" in response_json
+    assert len(response_json["translatedText"]) > 0
+
+
+def test_auto_detect_fallback_zh_to_zt(client_with_zt):
+    response = client_with_zt.post("/translate", data={
+        "q": "你好世界",
+        "source": "auto",
+        "target": "en",
+        "format": "text"
+    })
+    
+    response_json = json.loads(response.data)
+    assert response.status_code == 200
+    assert "translatedText" in response_json
+    assert len(response_json["translatedText"]) > 0
+