Fix build error

app.py

@@ -3,7 +3,7 @@ import json
 import shutil
 import socket
 from pathlib import Path
-from typing import Any, Dict, List, Optional
+from typing import Any, Dict, Generator, List, Optional
 
 from fastapi.responses import FileResponse, HTMLResponse, JSONResponse
 from fastapi.staticfiles import StaticFiles
@@ -122,7 +122,7 @@ def start_render_api(
     voice_config: Dict[str, Any],
     diffusion_steps: int = 32,
     speed: float = 1.0,
-):
+) -> Generator[Dict[str, Any], None, None]:
     job = pipeline.get_job(session_id)
     if job.status == "running":
         raise ValueError("A render is already active for this session")

tests/test_render_api.py

@@ -0,0 +1,15 @@
+import importlib
+import sys
+
+import gradio as gr
+
+
+def test_start_render_api_registers_one_streamed_output() -> None:
+    sys.modules.pop("app", None)
+    module = importlib.import_module("app")
+
+    with gr.Blocks() as demo:
+        dependency = gr.api(module.start_render_api, api_name="start_render")
+
+    assert dependency.get("outputs")
+    assert len(dependency["outputs"]) == 1