diff --git a/nlog/logs_test.go b/nlog/logs_test.go
index c965715..ac1d853 100644
--- a/nlog/logs_test.go
+++ b/nlog/logs_test.go
@@ -24,6 +24,10 @@ var (
 	_    Writer = (*mockWriter)(nil)
 )
 
+func init() {
+	ExitOnFatal.Set(false)
+}
+
 type mockWriter struct {
 	lock    sync.Mutex
 	builder strings.Builder
@@ -208,6 +212,12 @@ func TestFileLineConsoleMode(t *testing.T) {
 	assert.True(t, w.Contains(fmt.Sprintf("%s:%d", file, line+1)))
 }
 
+func TestMust(t *testing.T) {
+	assert.Panics(t, func() {
+		Must(errors.New("foo"))
+	})
+}
+
 func TestStructedLogAlert(t *testing.T) {
 	w := new(mockWriter)
 	old := writer.Swap(w)
@@ -574,26 +584,38 @@ func TestSetup(t *testing.T) {
 		atomic.StoreUint32(&encoding, jsonEncodingType)
 	}()
 
+	setupOnce = sync.Once{}
+	MustSetup(LogConf{
+		ServiceName: "any",
+		Mode:        "console",
+		Encoding:    "json",
+		TimeFormat:  timeFormat,
+	})
+	setupOnce = sync.Once{}
 	MustSetup(LogConf{
 		ServiceName: "any",
 		Mode:        "console",
 		TimeFormat:  timeFormat,
 	})
+	setupOnce = sync.Once{}
 	MustSetup(LogConf{
 		ServiceName: "any",
 		Mode:        "file",
 		Path:        os.TempDir(),
 	})
+	setupOnce = sync.Once{}
 	MustSetup(LogConf{
 		ServiceName: "any",
 		Mode:        "volume",
 		Path:        os.TempDir(),
 	})
+	setupOnce = sync.Once{}
 	MustSetup(LogConf{
 		ServiceName: "any",
 		Mode:        "console",
 		TimeFormat:  timeFormat,
 	})
+	setupOnce = sync.Once{}
 	MustSetup(LogConf{
 		ServiceName: "any",
 		Mode:        "console",
diff --git a/nlog/rotatelogger.go b/nlog/rotatelogger.go
index 22c25c1..f340a64 100644
--- a/nlog/rotatelogger.go
+++ b/nlog/rotatelogger.go
@@ -234,7 +234,7 @@ func NewLogger(filename string, rule RotateRule, compress bool) (*RotateLogger,
 		rule:     rule,
 		compress: compress,
 	}
-	if err := l.init(); err != nil {
+	if err := l.initialize(); err != nil {
 		return nil, err
 	}
 
@@ -278,7 +278,7 @@ func (l *RotateLogger) getBackupFilename() string {
 	return l.backup
 }
 
-func (l *RotateLogger) init() error {
+func (l *RotateLogger) initialize() error {
 	l.backup = l.rule.BackupFileName()
 
 	if fileInfo, err := os.Stat(l.filename); err != nil {