diff --git a/wal/wal.go b/wal/wal.go
index 593d4e939..8dce3e4e7 100644
--- a/wal/wal.go
+++ b/wal/wal.go
@@ -51,7 +51,7 @@ func (w *WAL) writeInfo(id int64) error {
 		return err
 	}
 	if o != 0 || w.bw.Buffered() != 0 {
-		return fmt.Errorf("cannot write info at %d, expect 0", o)
+		return fmt.Errorf("cannot write info at %d, expect 0", max(o, int64(w.bw.Buffered())))
 	}
 	if err := w.writeInt64(infoType); err != nil {
 		return err
@@ -101,3 +101,10 @@ func (w *WAL) writeInt64(n int64) error {
 func (w *WAL) flush() error {
 	return w.bw.Flush()
 }
+
+func max(a, b int64) int64 {
+	if a > b {
+		return a
+	}
+	return b
+}
diff --git a/wal/wal_test.go b/wal/wal_test.go
index c79dfb420..e2b0ac688 100644
--- a/wal/wal_test.go
+++ b/wal/wal_test.go
@@ -3,7 +3,10 @@ package wal
 import (
 	"io/ioutil"
 	"os"
+	"path"
 	"testing"
+
+	"github.com/coreos/etcd/raft"
 )
 
 func TestNew(t *testing.T) {
@@ -30,3 +33,73 @@ func TestNew(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+
+func TestWriteEntry(t *testing.T) {
+	p := path.Join(os.TempDir(), "waltest")
+	w, err := New(p)
+	if err != nil {
+		t.Fatal(err)
+	}
+	e := &raft.Entry{1, 1, []byte{1}}
+	err = w.writeEntry(e)
+	if err != nil {
+		t.Fatal(err)
+	}
+	w.flush()
+
+	err = os.Remove(p)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestWriteInfo(t *testing.T) {
+	p := path.Join(os.TempDir(), "waltest")
+	w, err := New(p)
+	if err != nil {
+		t.Fatal(err)
+	}
+	id := int64(0xBEEF)
+	err = w.writeInfo(id)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// make sure we can only write info at the head of the wal file
+	// still in buffer
+	err = w.writeInfo(id)
+	if err == nil || err.Error() != "cannot write info at 24, expect 0" {
+		t.Errorf("err = %v, want cannot write info at 8, expect 0", err)
+	}
+
+	// flush to disk
+	w.flush()
+	err = w.writeInfo(id)
+	if err == nil || err.Error() != "cannot write info at 24, expect 0" {
+		t.Errorf("err = %v, want cannot write info at 8, expect 0", err)
+	}
+
+	err = os.Remove(p)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestWriteState(t *testing.T) {
+	p := path.Join(os.TempDir(), "waltest")
+	w, err := New(p)
+	if err != nil {
+		t.Fatal(err)
+	}
+	st := &raft.State{1, 1, 1}
+	err = w.writeState(st)
+	if err != nil {
+		t.Fatal(err)
+	}
+	w.flush()
+
+	err = os.Remove(p)
+	if err != nil {
+		t.Fatal(err)
+	}
+}