Simple ajax call not working in wordpress plugin

You have to put the name of your wp ajax action in your data when you do the ajax call.

I assume the ajax url is correct.

jQuery( document ).ready(function(){
//alert("Jquery Loaded");
  jQuery("#pub_search").click(function(){
    alert("You clicked");
            event.preventDefault();           
            var term= $("#sterm").val();
            console.log('your term send: '+term);
            var data = {'nwterm': term, 'action': 'litsearch'}            
           $.get(litsearch.ajaxurl, data, function(data){
            $("#container").html(data.response);
          });
        });
});

Also because you want to put a response in your html code you have to send something back from server.

Test.php

<?php 
class Testclass{
    function infotext(){
        $txt="This is a ajax response text";
        return $txt;
    }
}
 ?>

Pub.php

<?php
function litsearch(){
    $newterm = $_GET['nwterm'];
    $newtest = new Testclass();
    $data = array();
    if($newterm == $_GET['nwterm']){
        include('test.php');
        $newtest = new Testclass();
        $data['response'] = $newtest->infotext();
    }
    wp_send_json( $data );
}
add_action('wp_ajax_litsearch', 'litsearch');
add_action('wp_ajax_nopriv_litsearch', 'litsearch');
 ?>