fix(tests): match the OS bind error in the owned-proxy port-race retry (#44462)

* fix(tests): match the OS bind error in the owned-proxy port-race retry

* test(integration): keep the port-race predicate pure so its unit tests stay in-process

---------

Co-authored-by: mateo-berri <277851410+mateo-berri@users.noreply.github.com>

tests/integration/_support/process.py

@@ -1,3 +1,4 @@
+import errno
 import os
 import signal
 import socket
@@ -112,6 +113,7 @@ def _stop(process: subprocess.Popen[bytes]) -> None:
 
 
 _PORT_ATTEMPTS: Final = 3
+_BIND_COLLISION: Final = os.strerror(errno.EADDRINUSE)
 
 
 def _free_port() -> int:
@@ -142,8 +144,8 @@ def _launch(command: tuple[str, ...], root: Path, environment: Mapping[str, str]
     return _Launch(process, port, log_path)
 
 
-def _lost_port_race(launch: _Launch) -> bool:
-    return launch.process.poll() is not None and "address already in use" in launch.log.read_text()
+def _lost_port_race(exit_code: int | None, log: Path) -> bool:
+    return exit_code is not None and _BIND_COLLISION in log.read_text()
 
 
 def _wait_until_ready(launch: _Launch) -> None:
@@ -165,13 +167,14 @@ def _launch_until_bound(
     launch: Final = _launch(command, root, environment, output)
     try:
         _wait_until_ready(launch)
-        assert launch.process.poll() is None or (attempts > 1 and _lost_port_race(launch)), (
+        exit_code: Final = launch.process.poll()
+        assert exit_code is None or (attempts > 1 and _lost_port_race(exit_code, launch.log)), (
             "Owned proxy exited before readiness"
         )
     except BaseException:
         _stop(launch.process)
         raise
-    if launch.process.poll() is None:
+    if exit_code is None:
         return launch
     _stop(launch.process)
     return _launch_until_bound(command, root, environment, output, attempts - 1)

tests/unit/integration_support/test_process.py

@@ -0,0 +1,38 @@
+from __future__ import annotations
+
+import errno
+import importlib
+import os
+from pathlib import Path
+from types import ModuleType
+from typing import Final
+
+import pytest
+
+TESTS_DIR: Final = Path(__file__).resolve().parents[2]
+BIND_ERROR_LINE: Final = f"ERROR:    {OSError(errno.EADDRINUSE, os.strerror(errno.EADDRINUSE))}\n"
+UNRELATED_CRASH: Final = "Traceback (most recent call last):\nModuleNotFoundError: No module named 'litellm'\n"
+
+
+@pytest.fixture
+def process_module(monkeypatch: pytest.MonkeyPatch) -> ModuleType:
+    monkeypatch.syspath_prepend(str(TESTS_DIR))
+    return importlib.import_module("integration._support.process")
+
+
+def _written_log(directory: Path, text: str) -> Path:
+    log: Final = directory / "owned-proxy.log"
+    log.write_text(text)
+    return log
+
+
+def test_lost_port_race_matches_the_bind_error_the_server_logs(process_module: ModuleType, tmp_path: Path) -> None:
+    assert process_module._lost_port_race(1, _written_log(tmp_path, BIND_ERROR_LINE))
+
+
+def test_lost_port_race_ignores_an_exit_for_another_reason(process_module: ModuleType, tmp_path: Path) -> None:
+    assert not process_module._lost_port_race(1, _written_log(tmp_path, UNRELATED_CRASH))
+
+
+def test_lost_port_race_needs_the_process_to_have_exited(process_module: ModuleType, tmp_path: Path) -> None:
+    assert not process_module._lost_port_race(None, _written_log(tmp_path, BIND_ERROR_LINE))