void test_stack() {
  THStack *hs = new THStack("hs", "test");
  TH1I *h1 = new TH1I("h1","h1", 3, 1, 4);
  TH1I *h2 = new TH1I("h2","h2", 3, 1, 4);

  h1->Fill(2);
  h2->Fill(2);

  h1->SetFillColor(kRed);
  h1->SetMarkerStyle(21);
  h1->SetMarkerColor(kRed);

  h2->SetFillColor(kBlue);
  h2->SetMarkerStyle(21);
  h2->SetMarkerColor(kBlue);

  hs->Add(h1,"sames");
  hs->Add(h2,"sames");

  hs->Draw();

  c1->Update();
  c1->Modified();
}