Deflake the issue-1363 tests: wait for lifespan startup instead of sleeping

tests/issues/test_1363_race_condition_streamable_http.py

@@ -21,6 +21,7 @@
 from contextlib import asynccontextmanager
 
 import anyio
+import anyio.to_thread
 import httpx
 import pytest
 from starlette.applications import Starlette
@@ -68,6 +69,7 @@ def __init__(self, app: Starlette):
         super().__init__(daemon=True)
         self.app = app
         self._stop_event = threading.Event()
+        self._ready_event = threading.Event()
 
     def run(self) -> None:
         """Run the lifespan in a new event loop."""
@@ -78,12 +80,19 @@ async def run_lifespan():
             lifespan_context = getattr(self.app.router, "lifespan_context", None)
             assert lifespan_context is not None  # Tests always create apps with lifespan
             async with lifespan_context(self.app):
+                # Only signal readiness once lifespan startup has completed, i.e. the
+                # session manager's task group exists and requests can be handled.
+                self._ready_event.set()
                 # Wait until stop is requested
                 while not self._stop_event.is_set():
                     await anyio.sleep(0.1)
 
         anyio.run(run_lifespan)
 
+    def wait_ready(self, timeout: float = 5.0) -> None:
+        """Block until the lifespan has started; call from a worker thread, not the event loop."""
+        assert self._ready_event.wait(timeout), "server thread did not start its lifespan in time"
+
     def stop(self) -> None:
         """Signal the thread to stop."""
         self._stop_event.set()
@@ -132,8 +141,8 @@ async def test_race_condition_invalid_accept_headers(caplog: pytest.LogCaptureFi
     server_thread.start()
 
     try:
-        # Give the server thread a moment to start
-        await anyio.sleep(0.1)
+        # Wait for the server thread to enter the lifespan before sending requests
+        await anyio.to_thread.run_sync(server_thread.wait_ready)
 
         # Suppress WARNING logs (expected validation errors) and capture ERROR logs
         with caplog.at_level(logging.ERROR):
@@ -203,8 +212,8 @@ async def test_race_condition_invalid_content_type(caplog: pytest.LogCaptureFixt
     server_thread.start()
 
     try:
-        # Give the server thread a moment to start
-        await anyio.sleep(0.1)
+        # Wait for the server thread to enter the lifespan before sending requests
+        await anyio.to_thread.run_sync(server_thread.wait_ready)
 
         # Suppress WARNING logs (expected validation errors) and capture ERROR logs
         with caplog.at_level(logging.ERROR):
@@ -243,8 +252,8 @@ async def test_race_condition_message_router_async_for(caplog: pytest.LogCapture
     server_thread.start()
 
     try:
-        # Give the server thread a moment to start
-        await anyio.sleep(0.1)
+        # Wait for the server thread to enter the lifespan before sending requests
+        await anyio.to_thread.run_sync(server_thread.wait_ready)
 
         # Suppress WARNING logs (expected validation errors) and capture ERROR logs
         with caplog.at_level(logging.ERROR):