generation-aware playback statuses

internal/playback/state_test.go

@@ -1,11 +1,22 @@
 package playback
 
 import (
+	"context"
 	"errors"
 	"testing"
 	"time"
 )
 
+func TestGenerationContext(t *testing.T) {
+	if got := generationFromContext(context.Background()); got != 0 {
+		t.Fatalf("background generation = %d, want 0", got)
+	}
+	ctx := withGeneration(context.Background(), 42)
+	if got := generationFromContext(ctx); got != 42 {
+		t.Fatalf("generation = %d, want 42", got)
+	}
+}
+
 func TestStatusPreservesValues(t *testing.T) {
 	wantErr := errors.New("producer missing")
 	status := Status{