From 6fc1c971c77ffdcdc02d102dce6b2ec00155f7b8 Mon Sep 17 00:00:00 2001
From: PJ <ipriyanshujain@gmail.com>
Date: Mon, 1 Jun 2026 15:10:01 +0530
Subject: [PATCH] feat(testrun): inject seed into web bundle via
 SANDERLING_SEED define

---
 internal/testrun/testrun.go | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/internal/testrun/testrun.go b/internal/testrun/testrun.go
index d77e948..dc25e42 100644
--- a/internal/testrun/testrun.go
+++ b/internal/testrun/testrun.go
@@ -7,6 +7,7 @@ import (
 	"math/rand/v2"
 	"os"
 	"path/filepath"
+	"strconv"
 	"time"
 
 	"github.com/priyanshujain/sanderling/internal/android"
@@ -53,9 +54,11 @@ func Execute(ctx context.Context, options Options, stdout io.Writer) error {
 		aliases["@sanderling/spec/defaults"] = filepath.Join(base, "defaults/index.ts")
 		aliases["@sanderling/spec/defaults/properties"] = filepath.Join(base, "defaults/properties.ts")
 	}
+	seed := resolveSeed(options.Seed)
 	defines := map[string]string{
 		"SANDERLING_TEST_PHONE": os.Getenv("SANDERLING_TEST_PHONE"),
 		"SANDERLING_TEST_OTP":   os.Getenv("SANDERLING_TEST_OTP"),
+		"SANDERLING_SEED":       strconv.FormatInt(seed, 10),
 	}
 	bundle, err := bundler.Bundle(bundler.Options{
 		EntryFile: options.Spec,
@@ -101,10 +104,6 @@ func Execute(ctx context.Context, options Options, stdout io.Writer) error {
 		}
 	}
 
-	seed := options.Seed
-	if seed == 0 {
-		seed = time.Now().UnixNano()
-	}
 	verifierInstance, err := verifier.New(
 		verifier.WithRand(rand.New(rand.NewPCG(uint64(seed), 0))),
 		verifier.WithAppPackage(options.BundleID),
@@ -173,6 +172,16 @@ func Execute(ctx context.Context, options Options, stdout io.Writer) error {
 	return nil
 }
 
+// resolveSeed returns the configured seed, or a time-derived one when unset.
+// The same value seeds both the goja PRNG and the web bundle's SANDERLING_SEED
+// define, so a single run is reproducible across both runtimes.
+func resolveSeed(configured int64) int64 {
+	if configured != 0 {
+		return configured
+	}
+	return time.Now().UnixNano()
+}
+
 // resolveWebRuntimePath returns the path to pkg/spec/src/web-runtime.ts.
 // Tries the spec-API checkout first (so monorepo development works without
 // publishing the package), then falls back to a sibling of the resolved