Benchmark for StdWriter.Write

Signed-off-by: Alexandr Morozov <lk4d4@docker.com>

pkg/stdcopy/stdcopy_test.go

@@ -0,0 +1,20 @@
+package stdcopy
+
+import (
+	"bytes"
+	"io/ioutil"
+	"testing"
+)
+
+func BenchmarkWrite(b *testing.B) {
+	w := NewStdWriter(ioutil.Discard, Stdout)
+	data := []byte("Test line for testing stdwriter performance\n")
+	data = bytes.Repeat(data, 100)
+	b.SetBytes(int64(len(data)))
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		if _, err := w.Write(data); err != nil {
+			b.Fatal(err)
+		}
+	}
+}