MDL-79248 mod_quiz: Behat scenario interacts incorrectly with select

This test was using the click operator to select an option value, rather
than selecting the value with form field steps.

In addition I found that sometimes the way in which a WS is used to
make the change before a refresh leads to a random failure if the page
navigation happens too slowly.

mod/quiz/amd/src/modal_add_random_question.js

@@ -28,6 +28,7 @@ import * as Fragment from 'core/fragment';
 import * as Templates from 'core/templates';
 import * as FormChangeChecker from 'core_form/changechecker';
 import {call as fetchMany} from 'core/ajax';
+import Pending from 'core/pending';
 
 const SELECTORS = {
     EXISTING_CATEGORY_CONTAINER: '[data-region="existing-category-container"]',
@@ -318,6 +319,8 @@ export default class ModalAddRandomQuestion extends Modal {
         newcategory,
         parentcategory
     ) {
+        // We do not need to resolve this Pending because the form submission will result in a page redirect.
+        new Pending('mod-quiz/modal_add_random_questions');
         const call = {
             methodname: 'mod_quiz_add_random_questions',
             args: {

mod/quiz/tests/behat/editing_remove_multiple_questions.feature

@@ -282,8 +282,7 @@ Feature: Edit quiz page - remove multiple questions
     # Delete all questions in page. Page contains multiple questions.
     When I open the "last" add to quiz menu
     And I follow "a random question"
-    And I click on "menurandomcount" "select"
-    And I click on "3" "option"
+    And I set the field "Number of random questions" to "3"
     And I press "Add random question"
     And I click on "Select multiple items" "button"
     And I press "Select all"