fix(testrun): report a sidecar that dies at startup as the exit it was

internal/testrun/driver_test.go

@@ -4,7 +4,9 @@ import (
 	"context"
 	"errors"
 	"io"
+	"strings"
 	"testing"
+	"time"
 
 	"github.com/priyanshujain/sanderling/internal/driver"
 	"github.com/priyanshujain/sanderling/internal/driver/ioscompanion"
@@ -65,6 +67,76 @@ func TestBuildDriverSurfacesDeviceConstructionError(t *testing.T) {
 	}
 }
 
+// A sidecar that dies during startup leaves the health poll with nothing to
+// talk to, and reporting that as a deadline sends the reader after a gRPC
+// timeout instead of the exit that already happened.
+func TestAwaitSidecarReportsTheExitItSaw(t *testing.T) {
+	exited := make(chan error, 1)
+	exited <- errors.New("exit status 1")
+	close(exited)
+
+	err := awaitSidecar(
+		context.Background(),
+		"127.0.0.1:54321",
+		30*time.Second,
+		func(ctx context.Context) error { <-ctx.Done(); return ctx.Err() },
+		exited,
+	)
+	if err == nil {
+		t.Fatal("expected an error when the sidecar exits before it is healthy")
+	}
+	for _, want := range []string{
+		"sidecar exited before it answered a health check on 127.0.0.1:54321: exit status 1",
+		"check the sidecar output above",
+		"sanderling doctor --platform=android",
+	} {
+		if !strings.Contains(err.Error(), want) {
+			t.Errorf("error %q missing %q", err, want)
+		}
+	}
+}
+
+func TestAwaitSidecarTimeoutSaysOnlyWhatItObserved(t *testing.T) {
+	ctx, cancel := context.WithTimeout(context.Background(), 50*time.Millisecond)
+	defer cancel()
+
+	err := awaitSidecar(
+		ctx,
+		"127.0.0.1:54321",
+		50*time.Millisecond,
+		func(ctx context.Context) error { <-ctx.Done(); return ctx.Err() },
+		make(chan error, 1),
+	)
+	if err == nil {
+		t.Fatal("expected an error when the sidecar never answers")
+	}
+	for _, want := range []string{
+		"sidecar did not answer a health check on 127.0.0.1:54321 within 50ms and is still running",
+		"check the sidecar output above",
+		"sanderling doctor --platform=android",
+	} {
+		if !strings.Contains(err.Error(), want) {
+			t.Errorf("error %q missing %q", err, want)
+		}
+	}
+	if strings.Contains(err.Error(), "context deadline exceeded") {
+		t.Errorf("error %q must not hand the reader a bare gRPC deadline", err)
+	}
+}
+
+func TestAwaitSidecarHealthyReturnsNil(t *testing.T) {
+	err := awaitSidecar(
+		context.Background(),
+		"127.0.0.1:54321",
+		30*time.Second,
+		func(context.Context) error { return nil },
+		make(chan error, 1),
+	)
+	if err != nil {
+		t.Fatalf("expected a healthy sidecar to pass, got %v", err)
+	}
+}
+
 // stubPreflight bypasses the host-readiness checks so routing tests exercise
 // driver construction on a Linux CI runner that lacks xcrun/java.
 func stubPreflight(t *testing.T) {