testing: add TB.TempDir

Fixes #35998

Change-Id: I87c6bf4e34e832be68862ca16ecfa6ea12048d31
Reviewed-on: https://go-review.googlesource.com/c/go/+/226877
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

1 files changed, 48 insertions, 0 deletions

diff --git a/src/testing/testing_test.go b/src/testing/testing_test.go
index 45e44683b4..afb35a96d4 100644
--- a/src/testing/testing_test.go
+++ b/src/testing/testing_test.go
@@ -5,6 +5,7 @@
 package testing_test
 
 import (
+	"io/ioutil"
 	"os"
 	"testing"
 )
@@ -16,3 +17,50 @@ import (
 func TestMain(m *testing.M) {
 	os.Exit(m.Run())
 }
+
+func TestTempDir(t *testing.T) {
+	dirCh := make(chan string, 1)
+	t.Cleanup(func() {
+		// Verify directory has been removed.
+		select {
+		case dir := <-dirCh:
+			fi, err := os.Stat(dir)
+			if os.IsNotExist(err) {
+				// All good
+				return
+			}
+			if err != nil {
+				t.Fatal(err)
+			}
+			t.Errorf("directory %q stil exists: %v, isDir=%v", dir, fi, fi.IsDir())
+		default:
+			if !t.Failed() {
+				t.Fatal("never received dir channel")
+			}
+		}
+	})
+
+	dir := t.TempDir()
+	if dir == "" {
+		t.Fatal("expected dir")
+	}
+	dir2 := t.TempDir()
+	if dir != dir2 {
+		t.Fatal("directory changed between calls")
+	}
+	dirCh <- dir
+	fi, err := os.Stat(dir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !fi.IsDir() {
+		t.Errorf("dir %q is not a dir", dir)
+	}
+	fis, err := ioutil.ReadDir(dir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(fis) > 0 {
+		t.Errorf("unexpected %d files in TempDir: %v", len(fis), fis)
+	}
+}