os: implement and smoketest os.Chmod

src/os/os_test.go

@@ -25,6 +25,32 @@ func newFile(testName string, t *testing.T) (f *File) {
 	return
 }
 
+func checkMode(t *testing.T, path string, mode FileMode) {
+	dir, err := Stat(path)
+	if err != nil {
+		t.Fatalf("Stat %q (looking for mode %#o): %s", path, mode, err)
+	}
+	if dir.Mode()&ModePerm != mode {
+		t.Errorf("Stat %q: mode %#o want %#o", path, dir.Mode(), mode)
+	}
+}
+
+func TestChmod(t *testing.T) {
+	f := newFile("TestChmod", t)
+	defer Remove(f.Name())
+	defer f.Close()
+	// Creation mode is read write
+
+	fm := FileMode(0456)
+	if runtime.GOOS == "windows" {
+		fm = FileMode(0444) // read-only file
+	}
+	if err := Chmod(f.Name(), fm); err != nil {
+		t.Fatalf("chmod %s %#o: %s", f.Name(), fm, err)
+	}
+	checkMode(t, f.Name(), fm)
+}
+
 func TestReadAt(t *testing.T) {
 	if runtime.GOOS == "windows" {
 		t.Log("TODO: implement Pread for Windows")