fix(benchmark): confirm target removal after close races

moli-benchmark/moli_benchmark/wpt_cross/runner.py

@@ -259,7 +259,14 @@ def _target_ids(infos: list[dict[str, Any]]) -> frozenset[str]:
 
 async def _close_target(client: RawCdpClient, target_id: str) -> None:
     command_id = await client.send("Target.closeTarget", {"targetId": target_id})
-    response, _ = await client.recv_until_id(command_id, timeout=5)
+    try:
+        response, _ = await client.recv_until_id(command_id, timeout=5)
+    except RawCdpError:
+        # Another target/context cleanup can win this race. Confirm that the
+        # requested target is gone before accepting the close failure.
+        if target_id not in _target_ids(await _target_infos(client)):
+            return
+        raise
     success = (response.get("result") or {}).get("success")
     if success is False:
         raise RawCdpError(f"Target.closeTarget rejected target {target_id}")

moli-benchmark/tests/test_wpt_target_cleanup.py

@@ -0,0 +1,31 @@
+import unittest
+from types import SimpleNamespace
+from unittest.mock import AsyncMock
+
+from moli_benchmark.raw_cdp import RawCdpError
+from moli_benchmark.wpt_cross.runner import _close_target
+
+
+class WptTargetCloseRaceTests(unittest.IsolatedAsyncioTestCase):
+    async def test_concurrent_target_removal_is_accepted_after_confirmation(self):
+        client = SimpleNamespace(
+            send=AsyncMock(side_effect=[1, 2]),
+            recv_until_id=AsyncMock(side_effect=[
+                RawCdpError("No target with given id found"),
+                ({"result": {"targetInfos": [{"targetId": "unrelated"}]}}, []),
+            ]),
+        )
+        await _close_target(client, "case-target")
+
+    async def test_close_errors_for_a_live_target_are_preserved(self):
+        error = RawCdpError("close rejected")
+        client = SimpleNamespace(
+            send=AsyncMock(side_effect=[1, 2]),
+            recv_until_id=AsyncMock(side_effect=[
+                error,
+                ({"result": {"targetInfos": [{"targetId": "case-target"}]}}, []),
+            ]),
+        )
+        with self.assertRaises(RawCdpError) as caught:
+            await _close_target(client, "case-target")
+        self.assertIs(caught.exception, error)