Automated test Run PHPUnit tests in user/tests/externallib_test.php. Manual test Using Chrome, login to your Moodle as an admin with some users enrolled using the MDK users script. Open the web inspector's Javascript console and paste in: require(['jquery', 'core/ajax'], function($, ajax, templates) { var doTest = function(value) { var webservice = 'core_user_get_users'; var promises = ajax.call([ { methodname: webservice, args: { "criteria": [   { "key": "firstname", "value": value + "%" }, { "key": "lastname", "value": value + "%" }   ], "mode": "loose" } } ]); promises[0] .done(function(response){ console.log(response); }); } // invoke tester doTest('ad') return doTest; }); Verify that one user is returned without warnings, and it's the admin user. Modify the parameter passed to doTest() to 'st' and paste it in again. Verify that 3 users are returned without warnings, and it's Stan, Butters and Bebe. Set the mode to "strict" and keep the parameter as 'st'. Verify that 0 users are returned without warnings.