[TESTS] auth LinkAccount test coverage

(cherry picked from commit e11dcc60f2)

use backticks to avoid backslash

(cherry picked from commit 34212791ee)
(cherry picked from commit bde9473c69)
(cherry picked from commit d4deb43084)
(cherry picked from commit 08e91649b0)

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)
+	}
+}