nodefs: check that default Create returns EROFS

nodefs/readonly_test.go

+// Copyright 2019 the Go-FUSE Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package nodefs
+
+import (
+	"syscall"
+	"testing"
+)
+
+func TestReadonlyCreate(t *testing.T) {
+	root := &Inode{}
+
+	mntDir, clean := testMount(t, root, nil)
+	defer clean()
+
+	_, err := syscall.Creat(mntDir+"/test", 0644)
+	if want := syscall.EROFS; want != err {
+		t.Fatalf("got err %v, want %v", err, want)
+	}
+}