diff --git a/Makefile b/Makefile
index 8c79b47..6192ad8 100644
--- a/Makefile
+++ b/Makefile
@@ -31,7 +31,8 @@ test: generate root
 	go test \
 		$(PKG)/tests \
 		$(PKG)/jlexer \
-		$(PKG)/gen
+		$(PKG)/gen \
+		$(PKG)/buffer
 	go test -benchmem -tags use_easyjson -bench . $(PKG)/benchmark
 
 bench-other: generate root
diff --git a/buffer/pool.go b/buffer/pool.go
index f539d4b..4de4a51 100644
--- a/buffer/pool.go
+++ b/buffer/pool.go
@@ -158,14 +158,14 @@ func (b *Buffer) Size() int {
 func (b *Buffer) DumpTo(w io.Writer) (written int, err error) {
 	var n int
 	for _, buf := range b.bufs {
-		if err != nil {
+		if err == nil {
 			n, err = w.Write(buf)
 			written += n
 		}
 		putBuf(buf)
 	}
 
-	if err != nil {
+	if err == nil {
 		n, err = w.Write(b.Buf)
 		written += n
 	}
diff --git a/buffer/pool_test.go b/buffer/pool_test.go
new file mode 100644
index 0000000..254ca6f
--- /dev/null
+++ b/buffer/pool_test.go
@@ -0,0 +1,79 @@
+package buffer
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestAppendByte(t *testing.T) {
+	var b Buffer
+	var want []byte
+
+	for i := 0; i < 1000; i++ {
+		b.AppendByte(1)
+		b.AppendByte(2)
+		want = append(want, 1, 2)
+	}
+
+	got := b.BuildBytes()
+	if !bytes.Equal(got, want) {
+		t.Errorf("BuildBytes() = %v; want %v", got, want)
+	}
+}
+
+func TestAppendBytes(t *testing.T) {
+	var b Buffer
+	var want []byte
+
+	for i := 0; i < 1000; i++ {
+		b.AppendBytes([]byte{1, 2})
+		want = append(want, 1, 2)
+	}
+
+	got := b.BuildBytes()
+	if !bytes.Equal(got, want) {
+		t.Errorf("BuildBytes() = %v; want %v", got, want)
+	}
+}
+
+func TestAppendString(t *testing.T) {
+	var b Buffer
+	var want []byte
+
+	s := "test"
+	for i := 0; i < 1000; i++ {
+		b.AppendBytes([]byte(s))
+		want = append(want, s...)
+	}
+
+	got := b.BuildBytes()
+	if !bytes.Equal(got, want) {
+		t.Errorf("BuildBytes() = %v; want %v", got, want)
+	}
+}
+
+func TestDumpTo(t *testing.T) {
+	var b Buffer
+	var want []byte
+
+	s := "test"
+	for i := 0; i < 1000; i++ {
+		b.AppendBytes([]byte(s))
+		want = append(want, s...)
+	}
+
+	out := &bytes.Buffer{}
+	n, err := b.DumpTo(out)
+	if err != nil {
+		t.Errorf("DumpTo() error: %v", err)
+	}
+
+	got := out.Bytes()
+	if !bytes.Equal(got, want) {
+		t.Errorf("DumpTo(): got %v; want %v", got, want)
+	}
+
+	if n != len(want) {
+		t.Errorf("DumpTo() = %v; want %v", n, len(want))
+	}
+}