Stabilize candidate-ordered recovery test

TESTING_GUIDE.md

@@ -81,6 +81,7 @@ Use the full suite by default. Use targeted filters only while iterating locally
 
 The test project mirrors the production areas closely.
 Use `docs/test-doc-maintenance-plan.md` before moving oversized suites or adding `Skip =` cases; it tracks the current split sequence, skip classifications, and large-document boundaries.
+Candidate-ordered parallel-index recovery tests must prove that the fatal result returns while the earlier contract candidate remains blocked and the parallel workers have not stopped. Assert those synchronization states instead of a narrow wall-clock threshold so the regression remains detectable under full-suite contention.
 
 - `ChunkSplitterTests.cs`, `SymbolExtractorTests.cs`, `ReferenceExtractorTests.cs`, `SearchSnippetFormatterTests.cs`, `DbPathResolverTests.cs`, `DbReaderUtilityTests.cs`, `ExcerptRecoveryCommandFormatterTests.cs`, `ConsoleUiTests.cs`
   Pure or mostly pure behavior tests with in-memory inputs.
@@ -1081,6 +1082,7 @@ dotnet test --filter "FullyQualifiedName~GitHelperTests"
 
 テストプロジェクトは、本番コードの責務にかなり近い形で分かれています。
 巨大 suite を移動する場合や `Skip =` case を追加する場合は、現在の分割順序、skip 分類、巨大ドキュメントの境界を追跡する `docs/test-doc-maintenance-plan.md` を先に確認してください。
+候補順序に基づく parallel index recovery のテストでは、先行する contract 候補が block されたまま、かつ parallel worker が停止する前に fatal result が返ることを検証してください。full-suite の競合下でも回帰を検出できるよう、狭い wall-clock threshold の代わりにこれらの同期状態を assertion にします。
 
 - `ChunkSplitterTests.cs`、`SymbolExtractorTests.cs`、`ReferenceExtractorTests.cs`、`SearchSnippetFormatterTests.cs`、`DbPathResolverTests.cs`、`DbReaderUtilityTests.cs`、`ExcerptRecoveryCommandFormatterTests.cs`、`ConsoleUiTests.cs`
   インメモリ入力中心の、純粋またはほぼ純粋な振る舞いのテスト。

changelog.d/unreleased/5063.internal.md

@@ -0,0 +1,16 @@
+---
+category: internal
+issues:
+  - 5063
+affected:
+  - tests/CodeIndex.Tests/IndexCommandRunnerUpdateTests.cs
+  - TESTING_GUIDE.md
+---
+
+## English
+
+- **Candidate-ordered recovery coverage now uses synchronization state (#5063)** — The parallel update regression test now proves that the fatal path returns while the earlier contract candidate remains blocked, avoiding a narrow wall-clock assertion under full-suite load.
+
+## 日本語
+
+- **候補順序回復のカバレッジを同期状態で検証するようにしました (#5063)** — 並列更新の回帰テストは、先行する contract 候補が block されたまま fatal path が返ることを検証し、full-suite 負荷の影響を受ける狭い wall-clock assertion を廃止しました。

tests/CodeIndex.Tests/IndexCommandRunnerUpdateTests.cs

@@ -3795,7 +3795,6 @@ public void Run_UpdateFiles_AuthoritativeCSharpParallelFatalDefersWhileEarlierCo
                 }
             };
 
-            var stopwatch = Stopwatch.StartNew();
             var (exitCode, json) = RunAndCaptureJson(
                 [
                     projectRoot,
@@ -3806,13 +3805,12 @@ public void Run_UpdateFiles_AuthoritativeCSharpParallelFatalDefersWhileEarlierCo
                     "--parallelism",
                     "2",
                 ]);
-            stopwatch.Stop();
 
             Assert.True(candidateWorkerEntered.IsSet);
             Assert.DoesNotContain("Source00.cs", completedExtractions.Keys);
-            Assert.True(
-                stopwatch.Elapsed < TimeSpan.FromSeconds(5),
-                $"The candidate-ordered serial recovery took {stopwatch.Elapsed}.");
+            Assert.False(
+                workersStopped.IsSet,
+                "The candidate-ordered parallel pipeline stopped before the earlier candidate was released.");
             Assert.Equal(CommandExitCodes.PartialResult, exitCode);
             Assert.Equal("partial", json.GetProperty("status").GetString());
             Assert.Equal(sourceZeroChecksum, ReadIndexedChecksum(dbPath, "Source00.cs"));