[TESTS] auth LinkAccount test coverage

(cherry picked from commit e11dcc60f2)

use backticks to avoid backslash

(cherry picked from commit 34212791ee)
(cherry picked from commit b76c67c99f)
(cherry picked from commit c3c21e3b6b)
(cherry picked from commit 9f4c722db4)
(cherry picked from commit e5360c908a)

tests/integration/linkaccount_test.go

@@ -0,0 +1,63 @@
+// Copyright 2023 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package integration
+
+import (
+	"net/http"
+	"testing"
+
+	gitea_context "code.gitea.io/gitea/modules/context"
+	"code.gitea.io/gitea/tests"
+
+	"github.com/markbates/goth"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestLinkAccountChoose(t *testing.T) {
+	defer tests.PrepareTestEnv(t)()
+	username := "linkaccountuser"
+	email := "linkaccountuser@example.com"
+	password := "linkaccountuser"
+	defer createUser(t, username, email, password)()
+
+	defer func() {
+		testMiddlewareHook = nil
+	}()
+
+	for _, testCase := range []struct {
+		gothUser  goth.User
+		signupTab string
+		signinTab string
+	}{
+		{
+			gothUser:  goth.User{},
+			signupTab: "item active",
+			signinTab: "item ",
+		},
+		{
+			gothUser: goth.User{
+				Email: email,
+			},
+			signupTab: "item ",
+			signinTab: "item active",
+		},
+	} {
+		testMiddlewareHook = func(ctx *gitea_context.Context) {
+			ctx.Session.Set("linkAccountGothUser", testCase.gothUser)
+		}
+
+		req := NewRequest(t, "GET", "/user/link_account")
+		resp := MakeRequest(t, req, http.StatusOK)
+		assert.Equal(t, resp.Code, http.StatusOK, resp.Body)
+		doc := NewHTMLParser(t, resp.Body)
+
+		class, exists := doc.Find(`.new-menu-inner .item[data-tab="auth-link-signup-tab"]`).Attr("class")
+		assert.True(t, exists, resp.Body)
+		assert.Equal(t, testCase.signupTab, class)
+
+		class, exists = doc.Find(`.new-menu-inner .item[data-tab="auth-link-signin-tab"]`).Attr("class")
+		assert.True(t, exists)
+		assert.Equal(t, testCase.signinTab, class)
+	}
+}