diff --git a/core/misc/ajax.es6.js b/core/misc/ajax.es6.js
index 72da2af326..8c59d13989 100644
--- a/core/misc/ajax.es6.js
+++ b/core/misc/ajax.es6.js
@@ -988,6 +988,9 @@
    *   {@link Drupal.Ajax} object created by {@link Drupal.ajax}.
    * @param {object} response
    *   The response from the Ajax request.
+   *
+   * @todo: Mark the function as deprecated after it will be possible. See
+   * https://www.drupal.org/project/drupal/issues/2973400
    */
   Drupal.theme.ajaxWrapperNewContent = ($newContent, ajax, response) => (
     (response.effect || ajax.effect) !== 'none' &&
@@ -1008,6 +1011,9 @@
    *
    * @param {jQuery} $elements
    *   Response elements after parsing.
+   *
+   * @todo: Mark the function as deprecated after it will be possible. See
+   * https://www.drupal.org/project/drupal/issues/2973400
    */
   Drupal.theme.ajaxWrapperMultipleRootElements = ($elements) => (
     $('<div class="wrapper-ajax-multiple-root-elements"></div>').append($elements)
@@ -1070,7 +1076,7 @@
       // Apply any settings from the returned JSON if available.
       const settings = response.settings || ajax.settings || drupalSettings;
 
-      // Parse response.data into an element collection.
+      // Parse response.data to get element collection.
       let $newContent = $('<div></div>').html(response.data).contents();
       $newContent = Drupal.theme('ajaxWrapperNewContent', $newContent, ajax, response);
 
diff --git a/core/modules/system/tests/modules/ajax_test/src/Controller/AjaxTestController.php b/core/modules/system/tests/modules/ajax_test/src/Controller/AjaxTestController.php
index eccc259874..68c85ad3d9 100644
--- a/core/modules/system/tests/modules/ajax_test/src/Controller/AjaxTestController.php
+++ b/core/modules/system/tests/modules/ajax_test/src/Controller/AjaxTestController.php
@@ -327,25 +327,33 @@ public function dialogClose() {
    *   Render types.
    */
   protected function getRenderTypes() {
-    $render_types = [
+    $render_single_root = [
       'pre-wrapped-div' => '<div class="pre-wrapped">pre-wrapped<script> var test;</script></div>',
       'pre-wrapped-span' => '<span class="pre-wrapped">pre-wrapped<script> var test;</script></span>',
       'pre-wrapped-whitespace' => ' <div class="pre-wrapped-whitespace">pre-wrapped-whitespace</div>' . "\r\n",
       'not-wrapped' => 'not-wrapped',
       'comment-string-not-wrapped' => '<!-- COMMENT -->comment-string-not-wrapped',
       'comment-not-wrapped' => '<!-- COMMENT --><div class="comment-not-wrapped">comment-not-wrapped</div>',
+      'svg' => '<svg xmlns="http://www.w3.org/2000/svg" width="10" height="10"><rect x="0" y="0" height="10" width="10" fill="green"/></svg>',
+      'empty' => '',
+    ];
+    $render_multiple_root = [
       'mixed' => ' foo <!-- COMMENT -->  foo bar<div class="a class"><p>some string</p></div> additional not wrapped strings, <!-- ANOTHER COMMENT --> <p>final string</p>',
       'top-level-only' => '<div>element #1</div><div>element #2</div>',
       'top-level-only-pre-whitespace' => ' <div>element #1</div><div>element #2</div> ',
       'top-level-only-middle-whitespace-span' => '<span>element #1</span> <span>element #2</span>',
       'top-level-only-middle-whitespace-div' => '<div>element #1</div> <div>element #2</div>',
-      'svg' => '<svg xmlns="http://www.w3.org/2000/svg" width="10" height="10"><rect x="0" y="0" height="10" width="10" fill="green"/></svg>',
-      'empty' => '',
     ];
-    foreach ($render_types as $key => $render) {
+
+    $render_info = [];
+    foreach ($render_single_root as $key => $render) {
       $render_info[$key] = ['render' => $render, 'effect' => 'fade'];
-      $render_info["$key--effect-none"] = ['render' => $render, 'effect' => 'none'];
     }
+    foreach ($render_multiple_root as $key => $render) {
+      $render_info[$key] = ['render' => $render, 'effect' => 'none'];
+      $render_info["$key--effect"] = ['render' => $render, 'effect' => 'fade'];
+    }
+
     return $render_info;
   }
 
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxTest.php
index 16b6e11aa2..80bddca2b7 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxTest.php
@@ -12,6 +12,9 @@
  */
 class AjaxTest extends JavascriptTestBase {
 
+  /**
+   * {@inheritdoc}
+   */
   protected $minkDefaultDriverClass = DrupalSelenium2Driver::class;
 
   /**
@@ -93,67 +96,40 @@ public function testDrupalSettingsCachingRegression() {
    * part of the context.
    */
   public function testInsertAjaxResponse() {
-    // Test that no additional wrapper is added when inserting already wrapped
-    // response data and all top-level node elements (context) are processed
-    // correctly.
-    $test_cases['pre-wrapped-div'] = '<div class="pre-wrapped processed">pre-wrapped<script> var test;</script></div>';
-    $test_cases['pre-wrapped-span'] = '<span class="pre-wrapped processed">pre-wrapped<script> var test;</script></span>';
-    // Test that no additional empty leading div is added when the return
-    // value had a leading space and all top-level node elements (context) are
-    // processed correctly.
-    $test_cases['pre-wrapped-whitespace'] = " <div class=\"pre-wrapped-whitespace processed\">pre-wrapped-whitespace</div>\n";
-    // Test that not wrapped response data (text node) is inserted not wrapped
-    // and all top-level node elements (context) are processed correctly.
-    $test_cases['not-wrapped'] = 'not-wrapped';
-    // Test that not wrapped response data (text node and comment node) is
-    // inserted wrapped and all top-level node elements
-    // (context) are processed correctly.
-    $test_cases['comment-string-not-wrapped'] = '<!-- COMMENT -->comment-string-not-wrapped';
-    // Test that top-level comments (which are not lead by text nodes) are
-    // inserted without wrapper.
-    $test_cases['comment-not-wrapped'] = '<!-- COMMENT --><div class="comment-not-wrapped processed">comment-not-wrapped</div>';
-    // Test that mixed inline & block level elements and comments response data
-    // is inserted correctly.
-    $test_cases['mixed'] = ' foo <!-- COMMENT -->  foo bar<div class="a class processed"><p>some string</p></div> additional not wrapped strings, <!-- ANOTHER COMMENT --> <p class="processed">final string</p>';
-    // Test that when the response has only top-level node elements, they
-    // are processed properly without extra wrapping.
-    $test_cases['top-level-only'] = '<div class="processed">element #1</div><div class="processed">element #2</div>';
-    // Test that whitespaces at start or end don't wrap the response when
-    // there are multiple top-level nodes.
-    $test_cases['top-level-only-pre-whitespace'] = ' <div class="processed">element #1</div><div class="processed">element #2</div> ';
-    // Test when there are whitespaces between top-level divs.
-    $test_cases['top-level-only-middle-whitespace-div'] = '<div class="processed">element #1</div> <div class="processed">element #2</div>';
-    // Test when there are whitespaces between top-level spans.
-    $test_cases['top-level-only-middle-whitespace-span'] = '<span class="processed">element #1</span> <span class="processed">element #2</span>';
-    // Test that svg parsed correctly.
-    $test_cases['svg'] = '<svg xmlns="http://www.w3.org/2000/svg" width="10" height="10" class="processed"><rect x="0" y="0" height="10" width="10" fill="green"/></svg>';
-    // Test that empty response data.
-    $test_cases['empty'] = '';
-
-    foreach ($test_cases as $key => $render) {
-      $test_all_cases["$key--effect-none"] = $render;
-    }
-    $test_cases += $test_all_cases;
-
-    $multiple_root_cases = [
-      'mixed',
-      'top-level-only',
-      'top-level-only-pre-whitespace',
-      'top-level-only-middle-whitespace-div',
-      'top-level-only-middle-whitespace-span',
+    $render_single_root = [
+      'pre-wrapped-div' => '<div class="pre-wrapped">pre-wrapped<script> var test;</script></div>',
+      'pre-wrapped-span' => '<span class="pre-wrapped">pre-wrapped<script> var test;</script></span>',
+      'pre-wrapped-whitespace' => ' <div class="pre-wrapped-whitespace">pre-wrapped-whitespace</div>' . "\n",
+      'not-wrapped' => 'not-wrapped',
+      'comment-string-not-wrapped' => '<!-- COMMENT -->comment-string-not-wrapped',
+      'comment-not-wrapped' => '<!-- COMMENT --><div class="comment-not-wrapped">comment-not-wrapped</div>',
+      'svg' => '<svg xmlns="http://www.w3.org/2000/svg" width="10" height="10"><rect x="0" y="0" height="10" width="10" fill="green"/></svg>',
+      'empty' => '',
     ];
+    $render_multiple_root_unwrapper = [
+      'mixed' => ' foo <!-- COMMENT -->  foo bar<div class="a class"><p>some string</p></div> additional not wrapped strings, <!-- ANOTHER COMMENT --> <p>final string</p>',
+      'top-level-only' => '<div>element #1</div><div>element #2</div>',
+      'top-level-only-pre-whitespace' => ' <div>element #1</div><div>element #2</div> ',
+      'top-level-only-middle-whitespace-span' => '<span>element #1</span> <span>element #2</span>',
+      'top-level-only-middle-whitespace-div' => '<div>element #1</div> <div>element #2</div>',
+    ];
+    $render_multiple_root_wrapper = [];
+    foreach ($render_multiple_root_unwrapper as $key => $render) {
+      $render_multiple_root_wrapper["$key--effect"] = '<div class="wrapper-ajax-multiple-root-elements">' . $render . '</div>';
+    }
 
-    foreach ($test_cases as $render_type => $expected) {
-      if (in_array($render_type, $multiple_root_cases, TRUE)) {
-        $unprocessed_expected = str_replace([' class="processed"', ' processed'], '', $expected);
-        $expected = '<div class="wrapper-ajax-multiple-root-elements processed">' . $unprocessed_expected . '</div>';
-      }
-      // Checking default process of wrapping Ajax content.
-      $this->assertInsertBlock($render_type, $expected);
-      $this->assertInsertInline($render_type, $expected);
+    $expected_renders = array_merge(
+      $render_single_root,
+      $render_multiple_root_wrapper,
+      $render_multiple_root_unwrapper
+    );
+
+    // Checking default process of wrapping Ajax content.
+    foreach ($expected_renders as $render_type => $expected) {
+      $this->assertInsert($render_type, $expected);
     }
 
-    // Checking custom logic for wrapping Ajax content with multiple root.
+    // Checking custom ajaxWrapperMultipleRootElements wrapping.
     $custom_wrapper_multiple_root = <<<JS
     (function($, Drupal){
       Drupal.theme.ajaxWrapperMultipleRootElements = function (elements) {
@@ -161,11 +137,10 @@ public function testInsertAjaxResponse() {
       };
     }(jQuery, Drupal));
 JS;
-    $expected = '<div class="my-favorite-div processed"><span>element #1</span> <span>element #2</span></div>';
-    $this->assertInsertBlock('top-level-only-middle-whitespace-span', $expected, $custom_wrapper_multiple_root);
-    $this->assertInsertInline('top-level-only-middle-whitespace-span', $expected, $custom_wrapper_multiple_root);
+    $expected = '<div class="my-favorite-div"><span>element #1</span> <span>element #2</span></div>';
+    $this->assertInsert('top-level-only-middle-whitespace-span--effect', $expected, $custom_wrapper_multiple_root);
 
-    // Checking that we can fully control the process of wrapping Ajax content.
+    // Checking custom ajaxWrapperNewContent wrapping.
     $custom_wrapper_new_content = <<<JS
     (function($, Drupal){
       Drupal.theme.ajaxWrapperNewContent = function (elements) {
@@ -173,22 +148,22 @@ public function testInsertAjaxResponse() {
       };
     }(jQuery, Drupal));
 JS;
-    $expected = '<div class="div-wrapper-forever processed"></div>';
-    $this->assertInsertBlock('empty--effect-none', $expected, $custom_wrapper_new_content);
-    $this->assertInsertInline('empty--effect-none', $expected, $custom_wrapper_new_content);
+    $expected = '<div class="div-wrapper-forever"></div>';
+    $this->assertInsert('empty', $expected, $custom_wrapper_new_content);
   }
 
   /**
-   * Assert block insert.
+   * Assert insert.
    *
    * @param string $render_type
    *   Render type.
    * @param string $expected
    *   Expected result.
    * @param string $script
-   *   Script for theming multiple root elements.
+   *   Script for additional theming.
    */
-  public function assertInsertBlock($render_type, $expected, $script = '') {
+  public function assertInsert($render_type, $expected, $script = '') {
+    // Check insert to block element.
     $this->drupalGet('ajax-test/insert-block-wrapper');
     $this->getSession()->executeScript($script);
     $this->clickLink("Link html $render_type");
@@ -198,19 +173,8 @@ public function assertInsertBlock($render_type, $expected, $script = '') {
     $this->getSession()->executeScript($script);
     $this->clickLink("Link replaceWith $render_type");
     $this->assertWaitPageContains('<div class="ajax-target-wrapper">' . $expected . '</div>');
-  }
 
-  /**
-   * Assert inline insert.
-   *
-   * @param string $render_type
-   *   Render type.
-   * @param string $expected
-   *   Expected result.
-   * @param string $script
-   *   Script for theming multiple root elements.
-   */
-  public function assertInsertInline($render_type, $expected, $script = '') {
+    // Check insert to inline element.
     $this->drupalGet('ajax-test/insert-inline-wrapper');
     $this->getSession()->executeScript($script);
     $this->clickLink("Link html $render_type");
@@ -231,8 +195,8 @@ public function assertInsertInline($render_type, $expected, $script = '') {
   protected function assertWaitPageContains($expected) {
     $page = $this->getSession()->getPage();
     $this->assertTrue($page->waitFor(10, function () use ($page, $expected) {
-      // After the effects can remain empty styles.
-      $content = str_replace(' style=""', '', $page->getContent());
+      // Clear content from empty styles and "processed" classes after effect.
+      $content = str_replace([' class="processed"', ' processed', ' style=""'], '', $page->getContent());
       return stripos($content, $expected) !== FALSE;
     }), "Page contains expected value: $expected");
   }