testing/fstest: return base name from mapfs FileInfo.Name

Change-Id: I5a68389a68875dbb2f6875de3f64f63dd7ca1af7
Reviewed-on: https://go-review.googlesource.com/c/go/+/565055
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>

src/testing/fstest/mapfs.go

@@ -150,7 +150,7 @@ type mapFileInfo struct {
 	f    *MapFile
 }
 
-func (i *mapFileInfo) Name() string               { return i.name }
+func (i *mapFileInfo) Name() string               { return path.Base(i.name) }
 func (i *mapFileInfo) Size() int64                { return int64(len(i.f.Data)) }
 func (i *mapFileInfo) Mode() fs.FileMode          { return i.f.Mode }
 func (i *mapFileInfo) Type() fs.FileMode          { return i.f.Mode.Type() }

src/testing/fstest/mapfs_test.go

@@ -45,3 +45,15 @@ a/b.txt: -rw-rw-rw-
 		t.Errorf("MapFS modes want:\n%s\ngot:\n%s\n", want, got)
 	}
 }
+
+func TestMapFSFileInfoName(t *testing.T) {
+	m := MapFS{
+		"path/to/b.txt": &MapFile{},
+	}
+	info, _ := m.Stat("path/to/b.txt")
+	want := "b.txt"
+	got := info.Name()
+	if want != got {
+		t.Errorf("MapFS FileInfo.Name want:\n%s\ngot:\n%s\n", want, got)
+	}
+}