rewrite getOSRoot fsondisk test helper

kyaml/filesys/fsondisk_test.go

@@ -7,10 +7,12 @@ import (
 	"os"
 	"path/filepath"
 	"reflect"
+	"runtime"
 	"sort"
 	"testing"
 
 	"github.com/stretchr/testify/require"
+	"golang.org/x/sys/windows"
 )
 
 const dirMsg = "expected '%s' to be a dir"
@@ -58,7 +60,8 @@ func TestCleanedAbs_2(t *testing.T) {
 	req := require.New(t)
 	fSys, _ := makeTestDir(t)
 
-	root := getOSRoot(t)
+	root, err := getOSRoot()
+	req.NoError(err)
 	d, f, err := fSys.CleanedAbs(root)
 	req.NoError(err)
 	req.Equal(root, d.String())
@@ -122,7 +125,8 @@ func TestConfirmDirDisk(t *testing.T) {
 	err = os.Symlink(filepath.Join(wd, relDir), linkDir)
 	req.NoError(err)
 
-	root := getOSRoot(t)
+	root, err := getOSRoot()
+	req.NoError(err)
 	tests := map[string]*struct {
 		path     string
 		expected string
@@ -257,3 +261,12 @@ func TestReadFilesRealFS(t *testing.T) {
 		})
 	}
 }
+
+func getOSRoot() (string, error) {
+	if runtime.GOOS == "windows" {
+		sysDir, err := windows.GetSystemDirectory()
+		return filepath.VolumeName(sysDir) + `\`, err
+	} else {
+		return string(filepath.Separator), nil
+	}
+}