test: tolerate dependency stderr warnings

Author: he-yufeng

tests/interaction/transports/test_stdio.py

@@ -21,6 +21,7 @@
 import sys
 import tempfile
 from pathlib import Path
+from typing import TextIO, cast
 
 import anyio
 import pytest
@@ -71,7 +72,7 @@ async def collect(params: LoggingMessageNotificationParams) -> None:
                 # so the server module is measured. Empty when not running under coverage.
                 env={key: value for key, value in os.environ.items() if key.startswith("COVERAGE_")},
             ),
-            errlog=errlog,
+            errlog=cast(TextIO, errlog),
         )
 
         with anyio.fail_after(10):
@@ -92,7 +93,8 @@ async def collect(params: LoggingMessageNotificationParams) -> None:
     # seeing it proves the process exited on its own rather than via the transport's terminate
     # escalation, without a timing-based assertion. The capture itself proves stderr passthrough:
     # the transport routes the child's stderr to the caller's `errlog` without consuming it.
-    assert captured_stderr == snapshot("stdio-echo: clean exit\n")
+    # Prerelease Python/lowest-direct dependency runs may print warnings before the server marker.
+    assert captured_stderr.endswith("stdio-echo: clean exit\n")
 
 
 @requirement("transport:stdio:stream-purity")