Add a simple test for external renderer (#20033)

Fix #16402

tests/integration/markup_external_test.go

@@ -0,0 +1,40 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package integration
+
+import (
+	"bytes"
+	"io"
+	"net/http"
+	"strings"
+	"testing"
+
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/tests"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestExternalMarkupRenderer(t *testing.T) {
+	defer tests.PrepareTestEnv(t)()
+	if !setting.Database.UseSQLite3 {
+		t.Skip()
+		return
+	}
+
+	const repoURL = "user30/renderer"
+	req := NewRequest(t, "GET", repoURL+"/src/branch/master/README.html")
+	resp := MakeRequest(t, req, http.StatusOK)
+	assert.EqualValues(t, "text/html; charset=UTF-8", resp.Header()["Content-Type"][0])
+
+	bs, err := io.ReadAll(resp.Body)
+	assert.NoError(t, err)
+
+	doc := NewHTMLParser(t, bytes.NewBuffer(bs))
+	div := doc.Find("div.file-view")
+	data, err := div.Html()
+	assert.NoError(t, err)
+	assert.EqualValues(t, "<div>\n\ttest external renderer\n</div>", strings.TrimSpace(data))
+}