3 files changed, 39 insertions, 2 deletions
diff --git a/src/testing/fstest/mapfs.go b/src/testing/fstest/mapfs.go
index 9fef2f4696..056ef133fa 100644
--- a/src/testing/fstest/mapfs.go
+++ b/src/testing/fstest/mapfs.go
@@ -66,7 +66,9 @@ func (fsys MapFS) Open(name string) (fs.File, error) {
 		for fname, f := range fsys {
 			i := strings.Index(fname, "/")
 			if i < 0 {
-				list = append(list, mapFileInfo{fname, f})
+				if fname != "." {
+					list = append(list, mapFileInfo{fname, f})
+				}
 			} else {
 				need[fname[:i]] = true
 			}
diff --git a/src/testing/fstest/mapfs_test.go b/src/testing/fstest/mapfs_test.go
index 2abedd6735..c8d29283b2 100644
--- a/src/testing/fstest/mapfs_test.go
+++ b/src/testing/fstest/mapfs_test.go
@@ -5,6 +5,9 @@
 package fstest
 
 import (
+	"fmt"
+	"io/fs"
+	"strings"
 	"testing"
 )
 
@@ -17,3 +20,28 @@ func TestMapFS(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+
+func TestMapFSChmodDot(t *testing.T) {
+	m := MapFS{
+		"a/b.txt": &MapFile{Mode: 0666},
+		".":       &MapFile{Mode: 0777 | fs.ModeDir},
+	}
+	buf := new(strings.Builder)
+	fs.WalkDir(m, ".", func(path string, d fs.DirEntry, err error) error {
+		fi, err := d.Info()
+		if err != nil {
+			return err
+		}
+		fmt.Fprintf(buf, "%s: %v\n", path, fi.Mode())
+		return nil
+	})
+	want := `
+.: drwxrwxrwx
+a: d---------
+a/b.txt: -rw-rw-rw-
+`[1:]
+	got := buf.String()
+	if want != got {
+		t.Errorf("MapFS modes want:\n%s\ngot:\n%s\n", want, got)
+	}
+}
diff --git a/src/testing/testing.go b/src/testing/testing.go
index 7f78a7caf8..be21d643fd 100644
--- a/src/testing/testing.go
+++ b/src/testing/testing.go
@@ -277,6 +277,8 @@
 //		os.Exit(m.Run())
 //	}
 //
+// TestMain is a low-level primitive and should not be necessary for casual
+// testing needs, where ordinary test functions suffice.
 package testing
 
 import (
@@ -714,6 +716,7 @@ type TB interface {
 	Log(args ...interface{})
 	Logf(format string, args ...interface{})
 	Name() string
+	Setenv(key, value string)
 	Skip(args ...interface{})
 	SkipNow()
 	Skipf(format string, args ...interface{})
@@ -747,7 +750,11 @@ type T struct {
 
 func (c *common) private() {}
 
-// Name returns the name of the running test or benchmark.
+// Name returns the name of the running (sub-) test or benchmark.
+//
+// The name will include the name of the test along with the names of
+// any nested sub-tests. If two sibling sub-tests have the same name,
+// Name will append a suffix to guarantee the returned name is unique.
 func (c *common) Name() string {
 	return c.name
 }