diff --git a/logger/encoder_test.go b/logger/encoder_test.go
index 9020805..23cd8f1 100644
--- a/logger/encoder_test.go
+++ b/logger/encoder_test.go
@@ -8,6 +8,7 @@ import (
 	"github.com/stretchr/testify/mock"
 	"go.uber.org/zap/zapcore"
 	"runtime"
+	"strings"
 	"testing"
 	"time"
 )
@@ -23,100 +24,76 @@ func zapCaller() zapcore.EntryCaller {
 	}
 }
 
+// encoderTest is a helper function to test buffer output of mock encoder.
+func encoderTest(t *testing.T, exec func(*mocks.PrimitiveArrayEncoder), expect string) {
+	encoder := mocks.NewPrimitiveArrayEncoder(t)
+	encoder.On("AppendInt64", mock.Anything).Maybe() // only enroll used method
+	encoder.On("AppendString", mock.Anything).Maybe()
+
+	exec(encoder)
+	var values []string
+	for _, call := range encoder.Calls {
+		values = append(values, fmt.Sprintf("%v", call.Arguments.Get(0)))
+	}
+	assert.Equal(t, strings.Join(values, " "), expect)
+}
+
 func Test_getCaller(t *testing.T) {
 	caller := zapCaller()
-	assert.Equal(t, getCaller(caller, false), "logger/encoder_test")
-	assert.Equal(t, getCaller(caller, true), "logger/encoder_test.go:0")
-
 	caller.File = "Invalid Path"
 	assert.Equal(t, getCaller(caller, true), "unknown")
 	assert.Equal(t, getCaller(caller, false), "unknown")
+
+	assert.Equal(t, getCaller(zapCaller(), false), "logger/encoder_test")
+	assert.Equal(t, getCaller(zapCaller(), true), "logger/encoder_test.go:0")
 }
 
 func Test_timeEncoder(t *testing.T) {
-	{
-		encoder := mocks.NewPrimitiveArrayEncoder(t)
-		encoder.On("AppendString", mock.Anything).Once()
+	encoderTest(t, func(encoder *mocks.PrimitiveArrayEncoder) {
 		timeEncoder(testTime, encoder)
-		encoder.AssertCalled(t, "AppendString", "2000-01-01 00:00:00.000")
-	}
-	{
-		encoder := mocks.NewPrimitiveArrayEncoder(t)
-		encoder.On("AppendString", mock.Anything).Once()
+	}, "2000-01-01 00:00:00.000")
+
+	encoderTest(t, func(encoder *mocks.PrimitiveArrayEncoder) {
 		timeColoredEncoder(testTime, encoder)
-		exceptPrefix := "\x1b[36m" + logger.prefix + "\x1b[0m"
-		encoder.AssertCalled(t, "AppendString", exceptPrefix+" \x1b[90m2000-01-01 00:00:00.000\x1b[0m")
-	}
+	}, "\x1b[36m"+logger.prefix+"\x1b[0m \x1b[90m2000-01-01 00:00:00.000\x1b[0m")
 }
 
 func Test_callerEncoder(t *testing.T) {
-	logger.verbose = false
-	{
-		encoder := mocks.NewPrimitiveArrayEncoder(t)
-		encoder.On("AppendString", mock.Anything).Once()
-		callerEncoder(zapCaller(), encoder)
-		encoder.AssertCalled(t, "AppendString", "[logger/encoder_test]")
-	}
-	{
-		encoder := mocks.NewPrimitiveArrayEncoder(t)
-		encoder.On("AppendString", mock.Anything).Once()
-		callerColoredEncoder(zapCaller(), encoder)
-		encoder.AssertCalled(t, "AppendString", "\x1b[35m[logger/encoder_test]\x1b[0m")
+	verboseVal := logger.verbose
+	callerTest := func(entry func(zapcore.EntryCaller, zapcore.PrimitiveArrayEncoder), expect string) {
+		encoderTest(t, func(encoder *mocks.PrimitiveArrayEncoder) {
+			entry(zapCaller(), encoder)
+		}, expect)
 	}
 
+	logger.verbose = false
+	callerTest(callerEncoder, "[logger/encoder_test]")
+	callerTest(callerColoredEncoder, "\x1b[35m[logger/encoder_test]\x1b[0m")
+
 	logger.verbose = true
-	{
-		encoder := mocks.NewPrimitiveArrayEncoder(t)
-		encoder.On("AppendString", mock.Anything).Once()
-		callerEncoder(zapCaller(), encoder)
-		expectPrefix := fmt.Sprintf("[%d]", goid.Get())
-		encoder.AssertCalled(t, "AppendString", expectPrefix+" [logger/encoder_test.go:0]")
-	}
-	{
-		encoder := mocks.NewPrimitiveArrayEncoder(t)
-		encoder.On("AppendString", mock.Anything).Once()
-		callerColoredEncoder(zapCaller(), encoder)
-		expectPrefix := fmt.Sprintf("\x1b[34m[%d]\x1b[0m", goid.Get())
-		encoder.AssertCalled(t, "AppendString", expectPrefix+" \x1b[35m[logger/encoder_test.go:0]\x1b[0m")
-	}
+	gid := fmt.Sprintf("[%d]", goid.Get())
+	callerTest(callerEncoder, gid+" [logger/encoder_test.go:0]")
+	callerTest(callerColoredEncoder, "\x1b[34m"+gid+"\x1b[0m \x1b[35m[logger/encoder_test.go:0]\x1b[0m")
+
+	logger.verbose = verboseVal
 }
 
 func Test_levelEncoder(t *testing.T) {
-	encoder := mocks.NewPrimitiveArrayEncoder(t)
-	enroll := func(values []string, call *mock.Call) *mock.Call {
-		for _, value := range values {
-			if call == nil {
-				call = encoder.On("AppendString", value).Once()
-			} else {
-				call = encoder.On("AppendString", value).Once().NotBefore(call)
-			}
-		}
-		return call
+	levelTest := func(entry func(zapcore.Level, zapcore.PrimitiveArrayEncoder), level zapcore.Level, expect string) {
+		encoderTest(t, func(encoder *mocks.PrimitiveArrayEncoder) {
+			entry(level, encoder)
+		}, expect)
 	}
 
-	caller := enroll([]string{
-		"[DEBUG]",
-		"[INFO]",
-		"[WARN]",
-		"[ERROR]",
-		"[PANIC]",
-	}, nil)
-	levelEncoder(zapcore.DebugLevel, encoder)
-	levelEncoder(zapcore.InfoLevel, encoder)
-	levelEncoder(zapcore.WarnLevel, encoder)
-	levelEncoder(zapcore.ErrorLevel, encoder)
-	levelEncoder(zapcore.PanicLevel, encoder)
-
-	enroll([]string{
-		"\x1b[39m[DEBUG]\x1b[0m",
-		"\x1b[32m[INFO]\x1b[0m",
-		"\x1b[33m[WARN]\x1b[0m",
-		"\x1b[31m[ERROR]\x1b[0m",
-		"\x1b[91m[PANIC]\x1b[0m",
-	}, caller)
-	levelColoredEncoder(zapcore.DebugLevel, encoder)
-	levelColoredEncoder(zapcore.InfoLevel, encoder)
-	levelColoredEncoder(zapcore.WarnLevel, encoder)
-	levelColoredEncoder(zapcore.ErrorLevel, encoder)
-	levelColoredEncoder(zapcore.PanicLevel, encoder)
+	levelTest(levelEncoder, zapcore.DebugLevel, "[DEBUG]")
+	levelTest(levelEncoder, zapcore.InfoLevel, "[INFO]")
+	levelTest(levelEncoder, zapcore.WarnLevel, "[WARN]")
+	levelTest(levelEncoder, zapcore.ErrorLevel, "[ERROR]")
+	levelTest(levelEncoder, zapcore.PanicLevel, "[PANIC]")
+
+	levelTest(levelColoredEncoder, zapcore.DebugLevel, "\x1b[39m[DEBUG]\x1b[0m")
+	levelTest(levelColoredEncoder, zapcore.InfoLevel, "\x1b[32m[INFO]\x1b[0m")
+	levelTest(levelColoredEncoder, zapcore.WarnLevel, "\x1b[33m[WARN]\x1b[0m")
+	levelTest(levelColoredEncoder, zapcore.ErrorLevel, "\x1b[31m[ERROR]\x1b[0m")
+	levelTest(levelColoredEncoder, zapcore.PanicLevel, "\x1b[91m[PANIC]\x1b[0m")
 }