gets the latest playtest from https://steamcommunity.com/groups/pcgameitplaytest/rss/ and request access to it.

pcgameitplaytest.user.js

// ==UserScript==
// @name         PCGameit Playtests
// @namespace    https://pcgameit.com
// @version      0.3
// @description  gets the latest playtest from https://steamcommunity.com/groups/pcgameitplaytest/rss/ and request access to it.
// @author       MalikQayum
// @connect      store.steampowered.com
// @connect      steamcommunity.com
// @match        https://store.steampowered.com/*
// @require     https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js
// @grant       GM_xmlhttpRequest
// @grant       GM_setValue
// @grant       GM_getValue
// @grant       GM_deleteValue
// @grant       unsafeWindow 
// ==/UserScript==

var notifyMe = 1; //set to 1 if you want to be notified that you made a request for a playtest and 0 off.

if( typeof GM_getValue("AppsRequested") === 'undefined' ){
    GM_setValue("AppsRequested", "[]");
}

unsafeWindow.ResetAppsRequested = function () {
     GM_setValue("AppsRequested", "[]"); //ResetAppsRequested(); in console if you want to reset the AppsRequested
}

GetPlaytestAppid();

function GetPlaytestAppid()
{
    GM_xmlhttpRequest({
        method: 'GET',
        url: 'https://steamcommunity.com/groups/pcgameitplaytest/rss/',
        headers: {
            'User-agent': 'Mozilla/4.0 (compatible) Greasemonkey/0.3',
            'Accept': 'application/atom+xml,application/xml,text/xml'
        },
        onload: function(response) {
            var dom = response.responseXML;
            var description_2 = dom.getElementsByTagName('description')[1].textContent;
            var appid = description_2.split("/")[4];
            console.log("parent appid: " + appid);
            CheckAppid(appid);
        }
    });
}

function CheckAppid(appid)
{
    console.log("here => " + JSON.parse(GM_getValue("AppsRequested")).length);
    if($.inArray(appid, JSON.parse(GM_getValue("AppsRequested"))) !== -1)
    {
        console.log("we have requested this before: " + JSON.parse(GM_getValue("AppsRequested")));
    }
    else
    {
        console.log("we have not requested this before: " + JSON.parse(GM_getValue("AppsRequested")));
        ajaxrequestplaytestaccess(appid);
    }
}

function ajaxrequestplaytestaccess(appid)
{
    var AppsRequestedArr = JSON.parse(GM_getValue("AppsRequested"));
    GM_xmlhttpRequest ({
        method: "POST",
        url: 'https://store.steampowered.com/ajaxrequestplaytestaccess/'+appid,
        data: "sessionid=" + g_sessionID,
        headers: {
            "Content-Type": "application/x-www-form-urlencoded"
        },
        onload: function(response)
        {
            response = JSON.parse(response.responseText);
            if(response.granted == 1)
            {
                console.log(appid +" => Instant Access.");
                AppsRequestedArr.push(appid);
                GM_setValue("AppsRequested", JSON.stringify(AppsRequestedArr));
                if(notifyMe == 1){ alert(appid +" => Instant Access."); }
            }
            else if(response.granted === null)
            {
                console.log(appid +" => Requested Access.");
                AppsRequestedArr.push(appid);
                GM_setValue("AppsRequested", JSON.stringify(AppsRequestedArr));
                if(notifyMe == 1){ alert(appid +" => Requested Access."); }
            }
            else
            {
                alert("something else => " + response);
            }
        }
    });
}