vpython: Add filesystem operation / test packages.

vpython/filesystem/testfs/tempdir.go

Index: vpython/filesystem/testfs/tempdir.go
diff --git a/vpython/filesystem/testfs/tempdir.go b/vpython/filesystem/testfs/tempdir.go
new file mode 100644
index 0000000000000000000000000000000000000000..96a05d5df71223620d080d0729eacfc17f0b372f
--- /dev/null
+++ b/vpython/filesystem/testfs/tempdir.go
@@ -0,0 +1,40 @@
+// Copyright 2017 The LUCI Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+package testfs
+
+import (
+	"io/ioutil"
+	"testing"
+
+	"github.com/luci/luci-go/vpython/filesystem"
+)
+
+// WithTempDir creates a temporary directory and passes it to fn. After fn
+// exits, the directory is cleaned up.
+func WithTempDir(t *testing.T, prefix string, fn func(string) error) error {
+	tdir, err := ioutil.TempDir("", prefix)
+	if err != nil {
+		return err
+	}
+	defer func() {
+		if rmErr := filesystem.RemoveAll(tdir); rmErr != nil {
+			t.Errorf("failed to remove temporary directory [%s]: %s", tdir, rmErr)
+		}
+	}()
+	return fn(tdir)
+}
+
+// MustWithTempDir calls WithTempDir and panics if any failures occur.
+func MustWithTempDir(t *testing.T, prefix string, fn func(string)) func() {
+	return func() {
+		err := WithTempDir(t, prefix, func(tdir string) error {
+			fn(tdir)
+			return nil
+		})
+		if err != nil {
+			panic(err)
+		}
+	}
+}