diff -u b/core/modules/system/tests/modules/ajax_test/js/insert-ajax.js b/core/modules/system/tests/modules/ajax_test/js/insert-ajax.js
--- b/core/modules/system/tests/modules/ajax_test/js/insert-ajax.js
+++ b/core/modules/system/tests/modules/ajax_test/js/insert-ajax.js
@@ -15,7 +15,7 @@
           wrapper: 'ajax-target',
           base: false,
           element: false,
-          method: 'html'
+          method: event.currentTarget.getAttribute('data-method')
         };
         var myAjaxObject = Drupal.ajax(ajaxSettings);
         myAjaxObject.execute();
diff -u b/core/modules/system/tests/modules/ajax_test/src/Controller/AjaxTestController.php b/core/modules/system/tests/modules/ajax_test/src/Controller/AjaxTestController.php
--- b/core/modules/system/tests/modules/ajax_test/src/Controller/AjaxTestController.php
+++ b/core/modules/system/tests/modules/ajax_test/src/Controller/AjaxTestController.php
@@ -51,34 +51,12 @@
    * @return array
    *   Renderable array of AJAX response contents.
    */
-  public static function renderTypes($type) {
-    switch ($type) {
-      case 'pre-wrapped':
-        $markup = '<div class="' . $type . '">' . $type . '</div>';
-        break;
-
-      case 'pre-wrapped-leading-whitespace':
-        $markup = ' <div class="' . $type . '">' . $type . '</div>';
-        break;
-
-      case 'not-wrapped':
-        $markup = $type;
-        break;
-
-      case 'comment-not-wrapped':
-        $markup = '<!-- COMMENT --><div class="' . $type . '">' . $type . '</div>';
-        break;
-
-      case 'mixed':
-        $markup = ' foo <!-- COMMENT -->  foo bar<div class="a class"><p>some string</p></div> additional not wrapped strings, <!-- ANOTHER COMMENT --> <p>final string</p>';
-        break;
-    }
-
+  public function renderTypes($type) {
     $content = [
       '#title' => '<em>AJAX Dialog & contents</em>',
       'content' => [
         '#type' => 'inline_template',
-        '#template' => !empty($markup) ? $markup : '',
+        '#template' => $this->getRenderTypes()[$type],
       ],
     ];
 
@@ -89,12 +67,9 @@
    * Returns a render array of links that directly Drupal.ajax().
    */
   public function insertLinks() {
-    $types = [
-      'pre-wrapped',
-      'pre-wrapped-leading-whitespace',
-      'not-wrapped',
-      'comment-not-wrapped',
-      'mixed',
+    $methods = [
+      'html',
+      'replaceWith',
     ];
 
     $build['links'] = [
@@ -106,17 +81,18 @@
         '#attached' => ['library' => ['ajax_test/ajax_insert']],
       ],
     ];
-
-    foreach ($types as $type) {
-      $build['links']['links']['#links'][$type] = [
-        'title' => "Link $type",
-        'url' => Url::fromRoute('ajax_test.ajax_render_types', ['type' => $type]),
-        'attributes' => [
-          'class' => ['ajax-insert'],
-        ],
-      ];
+    foreach ($methods as $method) {
+      foreach (array_keys($this->getRenderTypes()) as $type) {
+        $build['links']['links']['#links']["$method-$type"] = [
+          'title' => "Link $method $type",
+          'url' => Url::fromRoute('ajax_test.ajax_render_types', ['type' => $type]),
+          'attributes' => [
+            'class' => ['ajax-insert'],
+            'data-method' => $method,
+          ],
+        ];
+      }
     }
-
     return $build;
   }
 
@@ -303 +279,18 @@
+  /**
+   * Render types.
+   *
+   * @return array
+   *   Render types.
+   */
+  protected function getRenderTypes() {
+    return [
+      'pre-wrapped' => '<div class="pre-wrapped">pre-wrapped</div>',
+      'pre-wrapped-leading-whitespace' => ' <div class="pre-wrapped-leading-whitespace">pre-wrapped-leading-whitespace</div>',
+      'not-wrapped' => 'not-wrapped',
+      'comment-not-wrapped' => '<!-- COMMENT --><div class="comment-not-wrapped">comment-not-wrapped</div>',
+      'mixed' => ' foo <!-- COMMENT -->  foo bar<div class="a class"><p>some string</p></div> additional not wrapped strings, <!-- ANOTHER COMMENT --> <p>final string</p>',
+    ];
+  }
+
 }
+
diff -u b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxTest.php
--- b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxTest.php
@@ -104,39 +104,61 @@
    */
   public function testInsert() {
     $assert = $this->assertSession();
-    $this->drupalGet('ajax-test/insert');
 
-    // Test that no additional wrapper is added when inserting already wrapped
-    // response data and all top-level node elements (context) are processed
-    // correctly.
-    $this->clickLink('Link pre-wrapped');
-    $assert->assertWaitOnAjaxRequest();
-    $assert->responseContains($this->wrapAjaxTarget('<div class="pre-wrapped processed">pre-wrapped</div>'));
-
-    // 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.
-    $this->clickLink('Link pre-wrapped-leading-whitespace');
-    $assert->assertWaitOnAjaxRequest();
-    $assert->responseContains($this->wrapAjaxTarget('<div class="pre-wrapped-leading-whitespace processed">pre-wrapped-leading-whitespace</div>'));
-
-    // Test that not wrapped response data (text node) is inserted wrapped and
-    // all top-level node elements (context) are processed correctly.
-    $this->clickLink('Link not-wrapped');
-    $assert->assertWaitOnAjaxRequest();
-    $assert->responseContains($this->wrapAjaxTarget('<span class="processed">not-wrapped</span>'));
-
-    // Test that top-level comments (which are not lead by text nodes) are
-    // inserted without wrapper.
-    $this->clickLink('Link comment-not-wrapped');
-    $assert->assertWaitOnAjaxRequest();
-    $assert->responseContains($this->wrapAjaxTarget('<!-- COMMENT --><div class="comment-not-wrapped processed">comment-not-wrapped</div>'));
-
-    // Test that wrappend and not-wrapped response data is inserted correctly
-    // and all top-level node elements (context) are processed correctly.
-    $this->clickLink('Link mixed');
-    $assert->assertWaitOnAjaxRequest();
-    $assert->responseContains($this->wrapAjaxTarget('<span class="processed"> foo <!-- COMMENT -->  foo bar</span><div class="a class processed"><p>some string</p></div><span class="processed"> additional not wrapped strings, <!-- ANOTHER COMMENT --> </span><p class="processed">final string</p>'));
+    $test_cases = [
+      // Test that no additional wrapper is added when inserting already wrapped
+      // response data and all top-level node elements (context) are processed
+      // correctly.
+      [
+        'render_type' => 'pre-wrapped',
+        'expected' => '<div class="pre-wrapped processed">pre-wrapped</div>',
+      ],
+      // 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.
+      [
+        'render_type' => 'pre-wrapped-leading-whitespace',
+        'expected' => '<div class="pre-wrapped-leading-whitespace processed">pre-wrapped-leading-whitespace</div>',
+      ],
+      // Test that not wrapped response data (text node) is inserted wrapped and
+      // all top-level node elements (context) are processed correctly.
+      [
+        'render_type' => 'not-wrapped',
+        'expected' => '<span class="processed">not-wrapped</span>',
+      ],
+      // Test that top-level comments (which are not lead by text nodes) are
+      // inserted without wrapper.
+      [
+        'render_type' => 'comment-not-wrapped',
+        'expected' => '<!-- COMMENT --><div class="comment-not-wrapped processed">comment-not-wrapped</div>',
+      ],
+      // Test that wrappend and not-wrapped response data is inserted correctly
+      // and all top-level node elements (context) are processed correctly.
+      [
+        'method' => 'html',
+        'render_type' => 'mixed',
+        'expected' => '<span class="processed"> foo <!-- COMMENT -->  foo bar</span><div class="a class processed"><p>some string</p></div><span class="processed"> additional not wrapped strings, <!-- ANOTHER COMMENT --> </span><p class="processed">final string</p>',
+      ],
+
+    ];
+
+    foreach (['html', 'replaceWith'] as $method) {
+      foreach ($test_cases as $test_case) {
+        $this->drupalGet('ajax-test/insert');
+        $this->clickLink("Link $method {$test_case['render_type']}");
+        $assert->assertWaitOnAjaxRequest();
+        switch ($method) {
+          case 'html':
+            $assert->responseContains($this->wrapAjaxTarget($test_case['expected']));
+            break;
+
+          case 'replaceWith':
+            $assert->responseContains($test_case['expected']);
+            $assert->responseNotContains($this->wrapAjaxTarget($test_case['expected']));
+            break;
+        }
+      }
+    }
   }
 
 }