fixed signature check

api/gateway/mntx/internal/service/gateway/callback_test.go

@@ -1,6 +1,7 @@
 package gateway
 
 import (
+	"encoding/json"
 	"testing"
 	"time"
 
@@ -38,11 +39,11 @@ func TestMapCallbackToState_StatusMapping(t *testing.T) {
 	cfg := monetix.DefaultConfig()
 
 	cases := []struct {
-		name           string
-		paymentStatus  string
+		name            string
+		paymentStatus   string
 		operationStatus string
-		code           string
-		expectedStatus mntxv1.PayoutStatus
+		code            string
+		expectedStatus  mntxv1.PayoutStatus
 		expectedOutcome string
 	}{
 		{
@@ -119,12 +120,20 @@ func TestVerifyCallbackSignature(t *testing.T) {
 		t.Fatalf("failed to sign payload: %v", err)
 	}
 	cb.Signature = sig
-	if err := verifyCallbackSignature(cb, secret); err != nil {
+	payload, err := json.Marshal(cb)
+	if err != nil {
+		t.Fatalf("failed to marshal callback: %v", err)
+	}
+	if _, err := verifyCallbackSignature(payload, secret); err != nil {
 		t.Fatalf("expected valid signature, got %v", err)
 	}
 
 	cb.Signature = "invalid"
-	if err := verifyCallbackSignature(cb, secret); err == nil {
+	payload, err = json.Marshal(cb)
+	if err != nil {
+		t.Fatalf("failed to marshal callback: %v", err)
+	}
+	if _, err := verifyCallbackSignature(payload, secret); err == nil {
 		t.Fatalf("expected signature mismatch error")
 	}
 }