diff --git a/zap_text_core.go b/zap_text_core.go
index d2d426a..4148d52 100644
--- a/zap_text_core.go
+++ b/zap_text_core.go
@@ -20,25 +20,25 @@ import (
 	"go.uber.org/zap/zapcore"
 )
 
+// TextIOCore is a copy of zapcore.ioCore that only accept *textEncoder
+// it can be removed after https://github.com/uber-go/zap/pull/685 be merged
+type TextIOCore struct {
+	zapcore.LevelEnabler
+	enc zapcore.Encoder
+	out zapcore.WriteSyncer
+}
+
 // NewTextCore creates a Core that writes logs to a WriteSyncer.
 func NewTextCore(enc zapcore.Encoder, ws zapcore.WriteSyncer, enab zapcore.LevelEnabler) zapcore.Core {
-	return &textIOCore{
+	return &TextIOCore{
 		LevelEnabler: enab,
 		enc:          enc,
 		out:          ws,
 	}
 }
 
-// textIOCore is a copy of zapcore.ioCore that only accept *textEncoder
-// it can be removed after https://github.com/uber-go/zap/pull/685 be merged
-type textIOCore struct {
-	zapcore.LevelEnabler
-	enc zapcore.Encoder
-	out zapcore.WriteSyncer
-}
-
-func (c *textIOCore) With(fields []zapcore.Field) zapcore.Core {
-	clone := c.clone()
+func (c *TextIOCore) With(fields []zapcore.Field) zapcore.Core {
+	clone := c.Clone()
 	// it's different to ioCore, here call textEncoder#addFields to fix https://github.com/pingcap/log/issues/3
 	switch e := clone.enc.(type) {
 	case *textEncoder:
@@ -53,14 +53,14 @@ func (c *textIOCore) With(fields []zapcore.Field) zapcore.Core {
 	return clone
 }
 
-func (c *textIOCore) Check(ent zapcore.Entry, ce *zapcore.CheckedEntry) *zapcore.CheckedEntry {
+func (c *TextIOCore) Check(ent zapcore.Entry, ce *zapcore.CheckedEntry) *zapcore.CheckedEntry {
 	if c.Enabled(ent.Level) {
 		return ce.AddCore(ent, c)
 	}
 	return ce
 }
 
-func (c *textIOCore) Write(ent zapcore.Entry, fields []zapcore.Field) error {
+func (c *TextIOCore) Write(ent zapcore.Entry, fields []zapcore.Field) error {
 	buf, err := c.enc.EncodeEntry(ent, fields)
 	if err != nil {
 		return err
@@ -78,12 +78,12 @@ func (c *textIOCore) Write(ent zapcore.Entry, fields []zapcore.Field) error {
 	return nil
 }
 
-func (c *textIOCore) Sync() error {
+func (c *TextIOCore) Sync() error {
 	return c.out.Sync()
 }
 
-func (c *textIOCore) clone() *textIOCore {
-	return &textIOCore{
+func (c *TextIOCore) Clone() *TextIOCore {
+	return &TextIOCore{
 		LevelEnabler: c.LevelEnabler,
 		enc:          c.enc.Clone(),
 		out:          c.out,