diff --git a/components/engine/pkg/jsonlog/jsonlog_test.go b/components/engine/pkg/jsonlog/jsonlog_test.go
new file mode 100644
index 0000000000..5ee5eda35c
--- /dev/null
+++ b/components/engine/pkg/jsonlog/jsonlog_test.go
@@ -0,0 +1,61 @@
+package jsonlog
+
+import (
+	"bytes"
+	"encoding/json"
+	"io/ioutil"
+	"regexp"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/docker/docker/pkg/timeutils"
+)
+
+func TestWriteLog(t *testing.T) {
+	var buf bytes.Buffer
+	e := json.NewEncoder(&buf)
+	testLine := "Line that thinks that it is log line from docker\n"
+	for i := 0; i < 30; i++ {
+		e.Encode(JSONLog{Log: testLine, Stream: "stdout", Created: time.Now()})
+	}
+	w := bytes.NewBuffer(nil)
+	format := timeutils.RFC3339NanoFixed
+	if err := WriteLog(&buf, w, format); err != nil {
+		t.Fatal(err)
+	}
+	res := w.String()
+	t.Logf("Result of WriteLog: %q", res)
+	lines := strings.Split(strings.TrimSpace(res), "\n")
+	if len(lines) != 30 {
+		t.Fatalf("Must be 30 lines but got %d", len(lines))
+	}
+	logRe := regexp.MustCompile(`\[.*\] Line that thinks that it is log line from docker`)
+	for _, l := range lines {
+		if !logRe.MatchString(l) {
+			t.Fatalf("Log line not in expected format: %q", l)
+		}
+	}
+}
+
+func BenchmarkWriteLog(b *testing.B) {
+	var buf bytes.Buffer
+	e := json.NewEncoder(&buf)
+	testLine := "Line that thinks that it is log line from docker\n"
+	for i := 0; i < 30; i++ {
+		e.Encode(JSONLog{Log: testLine, Stream: "stdout", Created: time.Now()})
+	}
+	r := bytes.NewReader(buf.Bytes())
+	w := ioutil.Discard
+	format := timeutils.RFC3339NanoFixed
+	b.SetBytes(int64(r.Len()))
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		if err := WriteLog(r, w, format); err != nil {
+			b.Fatal(err)
+		}
+		b.StopTimer()
+		r.Seek(0, 0)
+		b.StartTimer()
+	}
+}