test: 添加 Gemini 流式解析和格式转换相关测试

- 添加 Gemini JSON-array 兜底解析测试
- 添加 Gemini stream_parser 单元测试
- 添加 provider transport URL 构建测试

tests/services/test_provider_transport.py

@@ -0,0 +1,65 @@
+from dataclasses import dataclass
+
+
+from src.services.provider.transport import build_provider_url
+
+
+@dataclass
+class _DummyEndpoint:
+    base_url: str
+    api_format: str
+    custom_path: str | None = None
+
+
+def test_gemini_stream_adds_alt_sse_and_drops_key_query_param() -> None:
+    endpoint = _DummyEndpoint(
+        base_url="https://generativelanguage.googleapis.com",
+        api_format="GEMINI",
+    )
+
+    url = build_provider_url(
+        endpoint,  # type: ignore[arg-type] - test stub
+        query_params={"key": "SECRET"},
+        path_params={"model": "gemini-1.5-pro"},
+        is_stream=True,
+    )
+
+    assert url.startswith(
+        "https://generativelanguage.googleapis.com/v1beta/models/gemini-1.5-pro:streamGenerateContent"
+    )
+    assert "key=" not in url
+    assert "alt=sse" in url
+
+
+def test_gemini_stream_does_not_override_existing_alt() -> None:
+    endpoint = _DummyEndpoint(
+        base_url="https://generativelanguage.googleapis.com",
+        api_format="GEMINI",
+    )
+
+    url = build_provider_url(
+        endpoint,  # type: ignore[arg-type] - test stub
+        query_params={"alt": "json"},
+        path_params={"model": "gemini-1.5-pro"},
+        is_stream=True,
+    )
+
+    assert "alt=json" in url
+    assert "alt=sse" not in url
+
+
+def test_gemini_non_stream_does_not_add_alt() -> None:
+    endpoint = _DummyEndpoint(
+        base_url="https://generativelanguage.googleapis.com",
+        api_format="GEMINI",
+    )
+
+    url = build_provider_url(
+        endpoint,  # type: ignore[arg-type] - test stub
+        path_params={"model": "gemini-1.5-pro"},
+        is_stream=False,
+    )
+
+    assert url.endswith("/v1beta/models/gemini-1.5-pro:generateContent")
+    assert "alt=" not in url
+