trunk-merge/pr-1788/833bc4de-83a5-4bfd-be2b-63e656dc2b7c-bisection

go/internal/runner/run_sweep_test.go

@@ -293,9 +293,10 @@ func TestRunReturnsNilWhenSweepCancelsContext(t *testing.T) {
 
 type blockingRemoveTestEngine struct {
 	*pipeRuntime
-	listed  chan struct{}
-	entered chan struct{}
-	removed chan struct{}
+	listed    chan struct{}
+	entered   chan struct{}
+	removed   chan struct{}
+	removeErr error // the ctx error Remove unwound on; read after removed closes
 }
 
 func (e *blockingRemoveTestEngine) ListByOwner(context.Context, string, string) ([]runtime.WorkloadID, error) {
@@ -306,8 +307,9 @@ func (e *blockingRemoveTestEngine) ListByOwner(context.Context, string, string)
 func (e *blockingRemoveTestEngine) Remove(ctx context.Context, _ runtime.WorkloadID) error {
 	close(e.entered)
 	<-ctx.Done()
+	e.removeErr = ctx.Err()
 	close(e.removed)
-	return ctx.Err()
+	return e.removeErr
 }
 
 type sessionsStartedTestHandler struct {
@@ -320,9 +322,9 @@ func (h *sessionsStartedTestHandler) Sessions(context.Context, *connect.BidiStre
 	return nil
 }
 
-func TestRunStartsSessionsBeforeStaleSweepDeadline(t *testing.T) {
+func TestRunStartsSessionsWhenStaleSweepTimesOut(t *testing.T) {
 	prev := staleContainerSweepTimeout
-	staleContainerSweepTimeout = 2 * time.Second
+	staleContainerSweepTimeout = 100 * time.Millisecond
 	t.Cleanup(func() { staleContainerSweepTimeout = prev })
 	handler := &sessionsStartedTestHandler{sessions: make(chan struct{})}
 	path, service := compassv1internalconnect.NewRunnerServiceHandler(handler)
@@ -340,11 +342,13 @@ func TestRunStartsSessionsBeforeStaleSweepDeadline(t *testing.T) {
 		removed:     make(chan struct{}),
 	}
 	ctx, cancel := context.WithCancel(t.Context())
-	done := make(chan error, 1)
+	runDone := make(chan struct{})
+	var runErr error
 	runtimeDir := shortRuntimeDir(t)
 	httpClient := h2cHTTPClient(t)
 	go func() {
-		done <- Run(ctx, RunnerConfig{
+		defer close(runDone)
+		runErr = Run(ctx, RunnerConfig{
 			RunnerID:   "runner-1",
 			ServerAddr: server.URL,
 			Token:      "tok",
@@ -353,43 +357,49 @@ func TestRunStartsSessionsBeforeStaleSweepDeadline(t *testing.T) {
 			HTTPClient: httpClient,
 		}, nil, discardLoggerRunner())
 	}()
-
-	select {
-	case <-handler.sessions:
-	case <-time.After(staleContainerSweepTimeout + time.Second):
+	// Registered after the timeout restore so it runs first: Run is joined
+	// before the var and runtime dir it reads are torn down.
+	t.Cleanup(func() {
 		cancel()
 		select {
-		case <-engine.removed:
+		case <-runDone:
 		case <-time.After(testTimeout):
-			t.Fatal("stale cleanup did not unwind after cancellation")
+			t.Error("Run did not return after cancellation")
 		}
-		select {
-		case <-done:
-		case <-time.After(testTimeout):
-			t.Fatal("Run did not return after cancellation")
-		}
-		t.Fatalf("Sessions did not start within %s while stale cleanup was blocked", staleContainerSweepTimeout+time.Second)
-	}
+	})
+
+	// Event-gated, no wall-clock bound asserted: the blocked Remove unwinds on the
+	// sweep's own deadline, then Sessions must start without any cancel.
 	select {
 	case <-engine.entered:
+	case <-runDone:
+		t.Fatalf("Run returned %v before the stale Remove started", runErr)
 	case <-time.After(testTimeout):
-		cancel()
 		t.Fatal("stale Remove did not start")
 	}
 	select {
 	case <-engine.removed:
 	case <-time.After(testTimeout):
 		t.Fatal("stale cleanup did not stop at its deadline")
 	}
+	if !errors.Is(engine.removeErr, context.DeadlineExceeded) {
+		t.Fatalf("stale Remove unwound on %v, want the sweep deadline", engine.removeErr)
+	}
+	select {
+	case <-handler.sessions:
+	case <-runDone:
+		t.Fatalf("Run returned %v before Sessions started", runErr)
+	case <-time.After(testTimeout):
+		t.Fatal("Sessions did not start after the stale sweep deadline")
+	}
 	select {
-	case err := <-done:
-		if err != nil {
-			t.Fatalf("Run after bounded startup sweep = %v, want nil", err)
+	case <-runDone:
+		if runErr != nil {
+			t.Fatalf("Run after bounded startup sweep = %v, want nil", runErr)
 		}
 	case <-time.After(testTimeout):
 		t.Fatal("Run did not return after Sessions completed")
 	}
-	cancel()
 }
 
 // The sweep reaches container backends only through a type assertion.