tests := map[string]testCase{
		"no_last_modified": {
			file:            "testdata/style.css",
			wantContentType: "text/css; charset=utf-8",
			wantStatus:      200,
		},
		"with_last_modified": {
			file:            "testdata/index.html",
			wantContentType: "text/html; charset=utf-8",
			modtime:         htmlModTime,
			wantLastMod:     htmlModTime.UTC().Format(TimeFormat),
			wantStatus:      200,