diff --git a/core/filex/file_test.go b/core/filex/file_test.go
index ed773d91..d79e06a8 100644
--- a/core/filex/file_test.go
+++ b/core/filex/file_test.go
@@ -74,6 +74,11 @@ func TestFirstLineShort(t *testing.T) {
 	assert.Equal(t, "first line", val)
 }
 
+func TestFirstLineError(t *testing.T) {
+	_, err := FirstLine("/tmp/does-not-exist")
+	assert.Error(t, err)
+}
+
 func TestLastLine(t *testing.T) {
 	filename, err := fs.TempFilenameWithText(text)
 	assert.Nil(t, err)
@@ -113,3 +118,8 @@ func TestLastLineWithLastNewlineShort(t *testing.T) {
 	assert.Nil(t, err)
 	assert.Equal(t, "last line", val)
 }
+
+func TestLastLineError(t *testing.T) {
+	_, err := LastLine("/tmp/does-not-exist")
+	assert.Error(t, err)
+}
diff --git a/core/logx/writer_test.go b/core/logx/writer_test.go
index ec5e8912..c88d0c7b 100644
--- a/core/logx/writer_test.go
+++ b/core/logx/writer_test.go
@@ -97,6 +97,15 @@ func TestConsoleWriter(t *testing.T) {
 	w.(*concreteWriter).statLog = easyToCloseWriter{}
 }
 
+func TestNewFileWriter(t *testing.T) {
+	t.Run("access", func(t *testing.T) {
+		_, err := newFileWriter(LogConf{
+			Path: "/not-exists",
+		})
+		assert.Error(t, err)
+	})
+}
+
 func TestNopWriter(t *testing.T) {
 	assert.NotPanics(t, func() {
 		var w nopWriter