names = append(names, f.Name)
		if _, err := f.Open(); err != nil {
			t.Errorf("Error opening %q: %v", f.Name, err)
		}
		if _, err := r.Open(f.Name); err == nil {
			t.Errorf("Opening %q with fs.FS API succeeded", f.Name)
		}
	}
	if !reflect.DeepEqual(names, entryNames) {
		t.Errorf("Unexpected file entries: %q", names)
	}
	if _, err := r.Open(""); err == nil {

		t.Fatal(err)
	}

	// read back zip file and check that we get to the end of it
	r, err := NewReader(buf, buf.Size())
	if err != nil {
		t.Fatal("reader:", err)
	}
	f0 := r.File[0]
	rc, err := f0.Open()
	if err != nil {
		t.Fatal("opening:", err)
	}
	rc.(*checksumReader).hash = fakeHash32{}
	for i := 0; i < chunks; i++ {
		_, err := io.ReadFull(rc, chunk)
		if err != nil {
			t.Fatal("read:", err)

		h, err := FileInfoHeader(info)
		if err != nil {
			return err
		}
		h.Name = name
		h.Method = Deflate
		fw, err := w.CreateHeader(h)
		if err != nil {
			return err
		}
		f, err := fsys.Open(name)
		if err != nil {
			return err
		}
		defer f.Close()
		_, err = io.Copy(fw, f)
		return err
	})
}

func (w *Writer) compressor(method uint16) Compressor {