Add benchmark for snapshot streams

internal/snapshotstream/stream_throughput_test.go

@@ -0,0 +1,50 @@
+package snapshotstream
+
+import (
+	"bytes"
+	"crypto/rand"
+	"testing"
+	"testing/fstest"
+
+	"github.com/hansmi/prombackup/api"
+)
+
+func BenchmarkStreamWriteTo(b *testing.B) {
+	const fileSize = 128 * 1024 * 1024
+
+	fileData := make([]byte, fileSize)
+
+	if _, err := rand.Read(fileData); err != nil {
+		b.Fatalf("Read() failed: %v", err)
+	}
+
+	root := fstest.MapFS{
+		"file": {
+			Data: fileData,
+		},
+	}
+
+	s, err := New(Options{
+		Name:   "stream",
+		Root:   root,
+		Format: api.ArchiveTar,
+	})
+	if err != nil {
+		b.Fatalf("New() failed: %v", err)
+	}
+
+	var buf bytes.Buffer
+
+	buf.Grow(fileSize)
+
+	b.SetBytes(fileSize)
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		if err := s.WriteTo(&buf); err != nil {
+			b.Errorf("WriteTo() failed: %v", err)
+		}
+
+		buf.Reset()
+	}
+}