chore: add more tests (#2547)

core/fs/files_test.go

@@ -0,0 +1,15 @@
+package fs
+
+import (
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCloseOnExec(t *testing.T) {
+	file := os.NewFile(0, os.DevNull)
+	assert.NotPanics(t, func() {
+		CloseOnExec(file)
+	})
+}