diff --git a/core/modules/book/tests/src/Kernel/BookMultilingualTest.php b/core/modules/book/tests/src/Kernel/BookMultilingualTest.php
index fbdfc3d8499a..73625a5a7068 100644
--- a/core/modules/book/tests/src/Kernel/BookMultilingualTest.php
+++ b/core/modules/book/tests/src/Kernel/BookMultilingualTest.php
@@ -174,7 +174,7 @@ class BookMultilingualTest extends KernelTestBase {
     $books = $bm->getAllBooks();
     $this->assertNotEmpty($books);
     foreach ($books as $book) {
-      $bid = $book['bid'];
+      $bid = (int) $book['bid'];
       $build = $bm->bookTreeOutput($bm->bookTreeAllData($bid));
       $items = $build['#items'];
       $this->assertBookItemIsCorrectlyTranslated($items[$bid], $langcode);
@@ -217,7 +217,7 @@ class BookMultilingualTest extends KernelTestBase {
     $bbb = $this->container->get('book.breadcrumb');
     $links = $bbb->build($route_match)->getLinks();
     $link = array_shift($links);
-    $rendered_link = Link::fromTextAndUrl($link->getText(), $link->getUrl())->toString();
+    $rendered_link = (string) Link::fromTextAndUrl($link->getText(), $link->getUrl())->toString();
     $this->assertStringContainsString("http://$langcode.book.test.domain/", $rendered_link);
     $link = array_shift($links);
     $this->assertNodeLinkIsCorrectlyTranslated(1, $link->getText(), $link->getUrl(), $langcode);
@@ -292,7 +292,7 @@ class BookMultilingualTest extends KernelTestBase {
    * @internal
    */
   protected function assertBookItemIsCorrectlyTranslated(array $item, string $langcode): void {
-    $this->assertNodeLinkIsCorrectlyTranslated($item['original_link']['nid'], $item['title'], $item['url'], $langcode);
+    $this->assertNodeLinkIsCorrectlyTranslated((int) $item['original_link']['nid'], $item['title'], $item['url'], $langcode);
   }
 
   /**
@@ -312,7 +312,7 @@ class BookMultilingualTest extends KernelTestBase {
   protected function assertNodeLinkIsCorrectlyTranslated(int $nid, string $title, Url $url, string $langcode): void {
     $node = Node::load($nid);
     $this->assertSame($node->getTranslation($langcode)->label(), $title);
-    $rendered_link = Link::fromTextAndUrl($title, $url)->toString();
+    $rendered_link = (string) Link::fromTextAndUrl($title, $url)->toString();
     $this->assertStringContainsString("http://$langcode.book.test.domain/node/$nid", $rendered_link);
   }
 
diff --git a/core/modules/content_moderation/tests/src/Kernel/DefaultRevisionStateTest.php b/core/modules/content_moderation/tests/src/Kernel/DefaultRevisionStateTest.php
index 9bb05d02d0b6..9ced54c900db 100644
--- a/core/modules/content_moderation/tests/src/Kernel/DefaultRevisionStateTest.php
+++ b/core/modules/content_moderation/tests/src/Kernel/DefaultRevisionStateTest.php
@@ -116,7 +116,7 @@ class DefaultRevisionStateTest extends KernelTestBase {
   /**
    * Verifies the expected moderation state revision exists.
    *
-   * @param int $revision_id
+   * @param string $revision_id
    *   The revision ID of the host entity.
    * @param string $langcode
    *   The language code of the host entity to check.
@@ -127,7 +127,7 @@ class DefaultRevisionStateTest extends KernelTestBase {
    *
    * @internal
    */
-  protected function assertModerationState(int $revision_id, string $langcode, string $expected_state, string $expected_workflow = 'editorial'): void {
+  protected function assertModerationState(string $revision_id, string $langcode, string $expected_state, string $expected_workflow = 'editorial'): void {
     $moderation_state_storage = $this->entityTypeManager->getStorage('content_moderation_state');
 
     $query = $moderation_state_storage->getQuery()->accessCheck(FALSE);
diff --git a/core/modules/content_moderation/tests/src/Kernel/WorkspacesContentModerationStateTest.php b/core/modules/content_moderation/tests/src/Kernel/WorkspacesContentModerationStateTest.php
index 6589ec00f199..9f9776682e5d 100644
--- a/core/modules/content_moderation/tests/src/Kernel/WorkspacesContentModerationStateTest.php
+++ b/core/modules/content_moderation/tests/src/Kernel/WorkspacesContentModerationStateTest.php
@@ -256,7 +256,7 @@ class WorkspacesContentModerationStateTest extends ContentModerationStateTest {
     // In the context of a workspace, the default revision ID is always the
     // latest workspace-specific revision, so we need to adjust the expectation
     // of the parent assertion.
-    $revision_id = $this->entityTypeManager->getStorage($entity->getEntityTypeId())->load($entity->id())->getRevisionId();
+    $revision_id = (int) $this->entityTypeManager->getStorage($entity->getEntityTypeId())->load($entity->id())->getRevisionId();
 
     // Additionally, the publishing status of the default revision is not
     // relevant in a workspace, because getting an entity to a "published"
diff --git a/core/modules/content_translation/tests/src/Kernel/ContentTranslationFieldSyncRevisionTest.php b/core/modules/content_translation/tests/src/Kernel/ContentTranslationFieldSyncRevisionTest.php
index a689935c413f..288f91eedfed 100644
--- a/core/modules/content_translation/tests/src/Kernel/ContentTranslationFieldSyncRevisionTest.php
+++ b/core/modules/content_translation/tests/src/Kernel/ContentTranslationFieldSyncRevisionTest.php
@@ -483,7 +483,7 @@ class ContentTranslationFieldSyncRevisionTest extends EntityKernelTestBase {
    *
    * @internal
    */
-  protected function assertLatestRevisionFieldValues(int $entity_id, array $expected_values): void {
+  protected function assertLatestRevisionFieldValues(string $entity_id, array $expected_values): void {
     /** @var \Drupal\Core\Entity\ContentEntityInterface $entity */
     $entity = $this->storage->loadRevision($this->storage->getLatestRevisionId($entity_id));
     @[$revision_id, $target_id_en, $target_id_it, $alt_en, $alt_it] = $expected_values;
diff --git a/core/modules/field/tests/src/Kernel/EntityReference/EntityReferenceFormatterTest.php b/core/modules/field/tests/src/Kernel/EntityReference/EntityReferenceFormatterTest.php
index 804f5ab97ece..14456f6aee1f 100644
--- a/core/modules/field/tests/src/Kernel/EntityReference/EntityReferenceFormatterTest.php
+++ b/core/modules/field/tests/src/Kernel/EntityReference/EntityReferenceFormatterTest.php
@@ -260,7 +260,7 @@ class EntityReferenceFormatterTest extends EntityKernelTestBase {
     // Check that the recursive rendering stops after it reaches the specified
     // limit.
     $build = $view_builder->view($referencing_entity_1, 'default');
-    $output = $renderer->renderRoot($build);
+    $output = (string) $renderer->renderRoot($build);
 
     // The title of entity_test entities is printed twice by default, so we have
     // to multiply the formatter's recursive rendering protection limit by 2.
@@ -279,14 +279,14 @@ class EntityReferenceFormatterTest extends EntityKernelTestBase {
     $referencing_entity_2->save();
 
     $build = $view_builder->view($referencing_entity_2, 'default');
-    $output = $renderer->renderRoot($build);
+    $output = (string) $renderer->renderRoot($build);
 
     $actual_occurrences = substr_count($output, $referencing_entity_2->label());
     $this->assertEquals($expected_occurrences, $actual_occurrences);
 
     // Now render both entities at the same time and check again.
     $build = $view_builder->viewMultiple([$referencing_entity_1, $referencing_entity_2], 'default');
-    $output = $renderer->renderRoot($build);
+    $output = (string) $renderer->renderRoot($build);
 
     $actual_occurrences = substr_count($output, $referencing_entity_1->label());
     $this->assertEquals($expected_occurrences, $actual_occurrences);
diff --git a/core/modules/field/tests/src/Kernel/EntityReference/Views/SelectionTest.php b/core/modules/field/tests/src/Kernel/EntityReference/Views/SelectionTest.php
index d9adda0c5690..8110e0c525ee 100644
--- a/core/modules/field/tests/src/Kernel/EntityReference/Views/SelectionTest.php
+++ b/core/modules/field/tests/src/Kernel/EntityReference/Views/SelectionTest.php
@@ -161,7 +161,7 @@ class SelectionTest extends KernelTestBase {
     foreach ($result as $node_type => $values) {
       foreach ($values as $nid => $label) {
         $this->assertSame($node_type, $this->nodes[$nid]->bundle());
-        $this->assertSame(trim(strip_tags($label)), Html::escape($this->nodes[$nid]->label()));
+        $this->assertSame(trim(strip_tags((string) $label)), Html::escape($this->nodes[$nid]->label()));
       }
     }
   }
diff --git a/core/modules/field/tests/src/Kernel/FieldDisplayTest.php b/core/modules/field/tests/src/Kernel/FieldDisplayTest.php
index 09801aea26b2..14d568f4fed9 100644
--- a/core/modules/field/tests/src/Kernel/FieldDisplayTest.php
+++ b/core/modules/field/tests/src/Kernel/FieldDisplayTest.php
@@ -115,8 +115,8 @@ class FieldDisplayTest extends KernelTestBase {
 
     $build = $this->display->build($entity);
     $renderer = \Drupal::service('renderer');
-    $content = $renderer->renderPlain($build);
-    $this->setRawContent((string) $content);
+    $content = (string) $renderer->renderPlain($build);
+    $this->setRawContent($content);
 
     $css_selector_converter = new CssSelectorConverter();
     $elements = $this->xpath($css_selector_converter->toXPath('.visually-hidden'));
diff --git a/core/modules/field/tests/src/Kernel/FieldKernelTestBase.php b/core/modules/field/tests/src/Kernel/FieldKernelTestBase.php
index a6dd4bae1cf5..f630209c7c76 100644
--- a/core/modules/field/tests/src/Kernel/FieldKernelTestBase.php
+++ b/core/modules/field/tests/src/Kernel/FieldKernelTestBase.php
@@ -155,7 +155,7 @@ abstract class FieldKernelTestBase extends KernelTestBase {
   protected function entityValidateAndSave(EntityInterface $entity) {
     $violations = $entity->validate();
     if ($violations->count()) {
-      $this->fail($violations);
+      $this->fail((string) $violations);
     }
     else {
       $entity->save();
diff --git a/core/modules/field/tests/src/Kernel/Views/HandlerFieldFieldTest.php b/core/modules/field/tests/src/Kernel/Views/HandlerFieldFieldTest.php
index 3e6f9d20fe7c..ce88f094663d 100644
--- a/core/modules/field/tests/src/Kernel/Views/HandlerFieldFieldTest.php
+++ b/core/modules/field/tests/src/Kernel/Views/HandlerFieldFieldTest.php
@@ -162,7 +162,7 @@ class HandlerFieldFieldTest extends KernelTestBase {
     // @see https://www.drupal.org/project/drupal/issues/3046722
     for ($i = 0; $i < 2; $i++) {
       $field_name = $this->fieldStorages[5]->getName();
-      $rendered_field = $view->style_plugin->getField($i, $field_name);
+      $rendered_field = (string) $view->style_plugin->getField($i, $field_name);
       $this->assertEquals(3, strlen(html_entity_decode($rendered_field)));
     }
   }
diff --git a/core/modules/file/tests/src/Kernel/FileManagedUnitTestBase.php b/core/modules/file/tests/src/Kernel/FileManagedUnitTestBase.php
index 990b5ef658cc..19ca6f584a01 100644
--- a/core/modules/file/tests/src/Kernel/FileManagedUnitTestBase.php
+++ b/core/modules/file/tests/src/Kernel/FileManagedUnitTestBase.php
@@ -97,7 +97,7 @@ abstract class FileManagedUnitTestBase extends KernelTestBase {
         $message = new FormattableMarkup('hook_file_@name was expected to be called %expected times but was called %actual times.', ['@name' => $hook, '%expected' => $expected_count, '%actual' => $actual_count]);
       }
     }
-    $this->assertEquals($expected_count, $actual_count, $message);
+    $this->assertEquals($expected_count, $actual_count, (string) $message);
   }
 
   /**
diff --git a/core/modules/file/tests/src/Kernel/Formatter/FileEntityFormatterTest.php b/core/modules/file/tests/src/Kernel/Formatter/FileEntityFormatterTest.php
index a32838bd650f..26c506dc9959 100644
--- a/core/modules/file/tests/src/Kernel/Formatter/FileEntityFormatterTest.php
+++ b/core/modules/file/tests/src/Kernel/Formatter/FileEntityFormatterTest.php
@@ -185,7 +185,7 @@ class FileEntityFormatterTest extends KernelTestBase {
       '#file' => $file,
     ];
 
-    $output = \Drupal::service('renderer')->renderRoot($file_link);
+    $output = (string) \Drupal::service('renderer')->renderRoot($file_link);
     $this->assertStringContainsString($this->fileUrlGenerator->generate('dummy-external-readonly://file-query-string?foo=bar')->toUriString(), $output);
   }
 
diff --git a/core/modules/image/tests/src/Kernel/ImageFormatterTest.php b/core/modules/image/tests/src/Kernel/ImageFormatterTest.php
index b2f67d1c4b29..0f7ee9404cb7 100644
--- a/core/modules/image/tests/src/Kernel/ImageFormatterTest.php
+++ b/core/modules/image/tests/src/Kernel/ImageFormatterTest.php
@@ -154,9 +154,9 @@ class ImageFormatterTest extends FieldKernelTestBase {
     $this->assertEquals('medium', $build[$this->fieldName][0]['#image_style']);
     // We check that the image URL contains the expected style directory
     // structure.
-    $this->assertStringContainsString('styles/medium/public/test-image.png', $build[$this->fieldName][0]['#markup']);
-    $this->assertStringContainsString('width="220"', $build[$this->fieldName][0]['#markup']);
-    $this->assertStringContainsString('height="220"', $build[$this->fieldName][0]['#markup']);
+    $this->assertStringContainsString('styles/medium/public/test-image.png', (string) $build[$this->fieldName][0]['#markup']);
+    $this->assertStringContainsString('width="220"', (string) $build[$this->fieldName][0]['#markup']);
+    $this->assertStringContainsString('height="220"', (string) $build[$this->fieldName][0]['#markup']);
 
     // The second image is an SVG, which is not supported by the GD toolkit.
     // The image style should still be applied with its cache tags, but image
@@ -167,11 +167,11 @@ class ImageFormatterTest extends FieldKernelTestBase {
     $this->assertEquals('medium', $build[$this->fieldName][1]['#image_style']);
     // We check that the image URL does not contain the style directory
     // structure.
-    $this->assertStringNotContainsString('styles/medium/public/test-image.svg', $build[$this->fieldName][1]['#markup']);
+    $this->assertStringNotContainsString('styles/medium/public/test-image.svg', (string) $build[$this->fieldName][1]['#markup']);
     // Since we did not store original image dimensions, width and height
     // HTML attributes will not be present.
-    $this->assertStringNotContainsString('width', $build[$this->fieldName][1]['#markup']);
-    $this->assertStringNotContainsString('height', $build[$this->fieldName][1]['#markup']);
+    $this->assertStringNotContainsString('width', (string) $build[$this->fieldName][1]['#markup']);
+    $this->assertStringNotContainsString('height', (string) $build[$this->fieldName][1]['#markup']);
   }
 
   /**
diff --git a/core/modules/node/tests/src/Kernel/Migrate/d7/MigrateNodeTest.php b/core/modules/node/tests/src/Kernel/Migrate/d7/MigrateNodeTest.php
index 55035a7419b7..ff1814d7fd0b 100644
--- a/core/modules/node/tests/src/Kernel/Migrate/d7/MigrateNodeTest.php
+++ b/core/modules/node/tests/src/Kernel/Migrate/d7/MigrateNodeTest.php
@@ -106,7 +106,7 @@ class MigrateNodeTest extends MigrateDrupal7TestBase {
    *
    * @internal
    */
-  protected function assertEntity(string $id, string $type, string $langcode, string $title, int $uid, bool $status, int $created, int $changed, bool $promoted, bool $sticky): void {
+  protected function assertEntity(int $id, string $type, string $langcode, string $title, int $uid, bool $status, int $created, int $changed, bool $promoted, bool $sticky): void {
     /** @var \Drupal\node\NodeInterface $node */
     $node = Node::load($id);
     $this->assertInstanceOf(NodeInterface::class, $node);
diff --git a/core/modules/search/tests/src/Kernel/SearchExcerptTest.php b/core/modules/search/tests/src/Kernel/SearchExcerptTest.php
index 3d740bb586d2..2c2bc79001ea 100644
--- a/core/modules/search/tests/src/Kernel/SearchExcerptTest.php
+++ b/core/modules/search/tests/src/Kernel/SearchExcerptTest.php
@@ -191,7 +191,7 @@ class SearchExcerptTest extends KernelTestBase {
    */
   protected function doSearchExcerpt($keys, $render_array, $langcode = NULL) {
     $render_array = search_excerpt($keys, $render_array, $langcode);
-    $text = \Drupal::service('renderer')->renderPlain($render_array);
+    $text = (string) \Drupal::service('renderer')->renderPlain($render_array);
     // The search_excerpt() function adds some extra spaces -- not
     // important for HTML formatting or this test. Remove these for comparison.
     return preg_replace('| +|', ' ', $text);
diff --git a/core/modules/system/tests/src/Kernel/Common/AddFeedTest.php b/core/modules/system/tests/src/Kernel/Common/AddFeedTest.php
index 8c9d8350ac04..eacb206d3e97 100644
--- a/core/modules/system/tests/src/Kernel/Common/AddFeedTest.php
+++ b/core/modules/system/tests/src/Kernel/Common/AddFeedTest.php
@@ -93,7 +93,7 @@ class AddFeedTest extends KernelTestBase {
       '#url' => 'node',
       '#title' => '<>&"\'',
     ];
-    $text = \Drupal::service('renderer')->renderRoot($variables);
+    $text = (string) \Drupal::service('renderer')->renderRoot($variables);
     $this->assertEquals('Subscribe to &lt;&gt;&amp;&quot;&#039;', trim(strip_tags($text)), 'feed_icon template escapes reserved HTML characters.');
   }
 
diff --git a/core/modules/system/tests/src/Kernel/Common/UrlTest.php b/core/modules/system/tests/src/Kernel/Common/UrlTest.php
index 9457ca8a8159..97e2dff93461 100644
--- a/core/modules/system/tests/src/Kernel/Common/UrlTest.php
+++ b/core/modules/system/tests/src/Kernel/Common/UrlTest.php
@@ -31,12 +31,12 @@ class UrlTest extends KernelTestBase {
     $path = "<SCRIPT>alert('XSS')</SCRIPT>";
     $encoded_path = "%3CSCRIPT%3Ealert%28%27XSS%27%29%3C/SCRIPT%3E";
 
-    $link = Link::fromTextAndUrl($text, Url::fromUserInput('/' . $path))->toString();
+    $link = (string) Link::fromTextAndUrl($text, Url::fromUserInput('/' . $path))->toString();
     $this->assertStringContainsString($encoded_path, $link, "XSS attack $path was filtered by \\Drupal\\Core\\Utility\\LinkGeneratorInterface::generate().");
     $this->assertStringNotContainsString($path, $link, "XSS attack $path was filtered by \\Drupal\\Core\\Utility\\LinkGeneratorInterface::generate().");
 
     // Test \Drupal\Core\Url.
-    $link = Url::fromUri('base:' . $path)->toString();
+    $link = (string) Url::fromUri('base:' . $path)->toString();
     $this->assertStringContainsString($encoded_path, $link, "XSS attack $path was filtered by #theme");
     $this->assertStringNotContainsString($path, $link, "XSS attack $path was filtered by #theme");
   }
@@ -95,17 +95,17 @@ class UrlTest extends KernelTestBase {
     $hreflang_override_link = $hreflang_link;
     $hreflang_override_link['#options']['attributes']['hreflang'] = 'foo';
 
-    $rendered = $renderer->renderRoot($hreflang_link);
+    $rendered = (string) $renderer->renderRoot($hreflang_link);
     $this->assertTrue($this->hasAttribute('hreflang', $rendered, $langcode), "hreflang attribute with value $langcode is present on a rendered link when langcode is provided in the render array.");
 
-    $rendered = $renderer->renderRoot($hreflang_override_link);
+    $rendered = (string) $renderer->renderRoot($hreflang_override_link);
     $this->assertTrue($this->hasAttribute('hreflang', $rendered, 'foo'), 'hreflang attribute with value foo is present on a rendered link when @hreflang is provided in the render array.');
 
     // Test adding a custom class in links produced by
     // \Drupal\Core\Utility\LinkGeneratorInterface::generate() and #type 'link'.
     // Test the link generator.
     $class_l = $this->randomMachineName();
-    $link_l = Link::fromTextAndUrl($this->randomMachineName(), Url::fromRoute('common_test.destination', [], ['attributes' => ['class' => [$class_l]]]))->toString();
+    $link_l = (string) Link::fromTextAndUrl($this->randomMachineName(), Url::fromRoute('common_test.destination', [], ['attributes' => ['class' => [$class_l]]]))->toString();
     $this->assertTrue($this->hasAttribute('class', $link_l, $class_l), "Custom class $class_l is present on link when requested by Link::toString()");
 
     // Test #type.
@@ -120,7 +120,7 @@ class UrlTest extends KernelTestBase {
         ],
       ],
     ];
-    $link_theme = $renderer->renderRoot($type_link);
+    $link_theme = (string) $renderer->renderRoot($type_link);
     $this->assertTrue($this->hasAttribute('class', $link_theme, $class_theme), "Custom class $class_theme is present on link when requested by #type");
   }
 
diff --git a/core/modules/system/tests/src/Kernel/Entity/EntityLabelTest.php b/core/modules/system/tests/src/Kernel/Entity/EntityLabelTest.php
index a29d454355ae..380b5fb1570d 100644
--- a/core/modules/system/tests/src/Kernel/Entity/EntityLabelTest.php
+++ b/core/modules/system/tests/src/Kernel/Entity/EntityLabelTest.php
@@ -41,11 +41,11 @@ class EntityLabelTest extends KernelTestBase {
       // string. Special cases may need to be added to this test in the future
       // if an acronym is in a different position in the label.
       $first_word = strtok($label_string, " ");
-      $remaining_string = strtolower(strstr($label_string, " "));
+      $remaining_string = strtolower((string) strstr($label_string, " "));
       $this->assertEquals($first_word . $remaining_string, $label_string);
 
       $first_word = strtok($collection_label_string, " ");
-      $remaining_string = strtolower(strstr($collection_label_string, " "));
+      $remaining_string = strtolower((string) strstr($collection_label_string, " "));
       $this->assertEquals($first_word . $remaining_string, $collection_label_string);
     }
   }
diff --git a/core/modules/taxonomy/tests/src/Kernel/TermKernelTest.php b/core/modules/taxonomy/tests/src/Kernel/TermKernelTest.php
index 8166e9a3f732..b0b4d4f5dc14 100644
--- a/core/modules/taxonomy/tests/src/Kernel/TermKernelTest.php
+++ b/core/modules/taxonomy/tests/src/Kernel/TermKernelTest.php
@@ -167,7 +167,7 @@ class TermKernelTest extends KernelTestBase {
     $this->assertNotEmpty($render_array, 'Term view builder is built.');
 
     // Confirm we can render said view.
-    $rendered = \Drupal::service('renderer')->renderPlain($render_array);
+    $rendered = (string) \Drupal::service('renderer')->renderPlain($render_array);
     $this->assertNotEmpty(trim($rendered), 'Term is able to be rendered.');
   }
 
diff --git a/core/modules/user/tests/src/Kernel/Migrate/d7/MigrateUserTest.php b/core/modules/user/tests/src/Kernel/Migrate/d7/MigrateUserTest.php
index 571c8c08bafc..1f4ff49057c6 100644
--- a/core/modules/user/tests/src/Kernel/Migrate/d7/MigrateUserTest.php
+++ b/core/modules/user/tests/src/Kernel/Migrate/d7/MigrateUserTest.php
@@ -194,10 +194,10 @@ class MigrateUserTest extends MigrateDrupal7TestBase {
         $source->name,
         $source->mail,
         $source->pass,
-        $source->created,
-        $source->access,
-        $source->login,
-        $source->status,
+        (int) $source->created,
+        (int) $source->access,
+        (int) $source->login,
+        (bool) $source->status,
         $entity_language,
         $source->language,
         $source->timezone,
diff --git a/core/modules/user/tests/src/Kernel/Views/HandlerFilterPermissionTest.php b/core/modules/user/tests/src/Kernel/Views/HandlerFilterPermissionTest.php
index f2c403cd593c..8c7bd1274f38 100644
--- a/core/modules/user/tests/src/Kernel/Views/HandlerFilterPermissionTest.php
+++ b/core/modules/user/tests/src/Kernel/Views/HandlerFilterPermissionTest.php
@@ -105,7 +105,7 @@ class HandlerFilterPermissionTest extends UserKernelTestBase {
     }
     foreach (['system' => 'System', 'user' => 'User'] as $module => $title) {
       $expected = array_map(function ($permission) {
-        return Html::escape(strip_tags($permission['title']));
+        return Html::escape(strip_tags((string) $permission['title']));
       }, $permission_by_module[$module]);
 
       $this->assertEquals($expected, $value_options[$title], 'Ensure the all permissions are available');
diff --git a/core/modules/views/tests/src/Kernel/Entity/RowEntityRenderersTest.php b/core/modules/views/tests/src/Kernel/Entity/RowEntityRenderersTest.php
index 12cfc35988e5..82516bc672c7 100644
--- a/core/modules/views/tests/src/Kernel/Entity/RowEntityRenderersTest.php
+++ b/core/modules/views/tests/src/Kernel/Entity/RowEntityRenderersTest.php
@@ -386,7 +386,7 @@ class RowEntityRenderersTest extends ViewsKernelTestBase {
     foreach ($expected as $index => $expected_output) {
       if (!empty($view->result[$index])) {
         $build = $view->rowPlugin->render($view->result[$index]);
-        $output = \Drupal::service('renderer')->renderRoot($build);
+        $output = (string) \Drupal::service('renderer')->renderRoot($build);
         $result = str_contains($output, $expected_output);
         if (!$result) {
           break;
diff --git a/core/modules/views/tests/src/Kernel/Handler/AreaEntityTest.php b/core/modules/views/tests/src/Kernel/Handler/AreaEntityTest.php
index 46304a776b65..c83022efa25d 100644
--- a/core/modules/views/tests/src/Kernel/Handler/AreaEntityTest.php
+++ b/core/modules/views/tests/src/Kernel/Handler/AreaEntityTest.php
@@ -172,7 +172,7 @@ class AreaEntityTest extends ViewsKernelTestBase {
     $this->setRawContent($renderer->renderRoot($preview));
     $view_class = 'js-view-dom-id-' . $view->dom_id;
     $result = $this->xpath('//div[@class = "' . $view_class . '"]/footer[1]');
-    $this->assertStringNotContainsString($entities[2]->label(), $result[0], 'The rendered entity does not appear in the footer of the view.');
+    $this->assertStringNotContainsString($entities[2]->label(), (string) $result[0], 'The rendered entity does not appear in the footer of the view.');
 
     // Test the available view mode options.
     $form = [];
diff --git a/core/modules/views/tests/src/Kernel/Handler/AreaTest.php b/core/modules/views/tests/src/Kernel/Handler/AreaTest.php
index 8e0dab1404ea..4d0e4f94d441 100644
--- a/core/modules/views/tests/src/Kernel/Handler/AreaTest.php
+++ b/core/modules/views/tests/src/Kernel/Handler/AreaTest.php
@@ -75,7 +75,7 @@ class AreaTest extends ViewsKernelTestBase {
 
     // Check whether the strings exist in the output and are sanitized.
     $output = $view->preview();
-    $output = $this->container->get('renderer')->renderRoot($output);
+    $output = (string) $this->container->get('renderer')->renderRoot($output);
     $this->assertStringContainsString(Xss::filterAdmin($header_string), $output, 'Views header exists in the output and is sanitized');
     $this->assertStringContainsString(Xss::filterAdmin($footer_string), $output, 'Views footer exists in the output and is sanitized');
     $this->assertStringContainsString(Xss::filterAdmin($empty_string), $output, 'Views empty exists in the output and is sanitized');
@@ -94,7 +94,7 @@ class AreaTest extends ViewsKernelTestBase {
     $this->assertCount(0, $handlers);
 
     $output = $view->preview();
-    $output = \Drupal::service('renderer')->renderRoot($output);
+    $output = (string) \Drupal::service('renderer')->renderRoot($output);
     // The area output should not be present since access was denied.
     $this->assertStringNotContainsString('a custom string', $output);
     $view->destroy();
@@ -116,7 +116,7 @@ class AreaTest extends ViewsKernelTestBase {
     $handlers = $view->display_handler->getHandlers('empty');
 
     $output = $view->preview();
-    $output = \Drupal::service('renderer')->renderRoot($output);
+    $output = (string) \Drupal::service('renderer')->renderRoot($output);
     $this->assertStringContainsString('a custom string', $output);
     $this->assertCount(1, $handlers);
   }
diff --git a/core/modules/views/tests/src/Kernel/Handler/AreaViewTest.php b/core/modules/views/tests/src/Kernel/Handler/AreaViewTest.php
index 5f566e7fd6d9..f33371a51574 100644
--- a/core/modules/views/tests/src/Kernel/Handler/AreaViewTest.php
+++ b/core/modules/views/tests/src/Kernel/Handler/AreaViewTest.php
@@ -40,14 +40,14 @@ class AreaViewTest extends ViewsKernelTestBase {
 
     $this->executeView($view);
     $output = $view->render();
-    $output = $renderer->renderRoot($output);
+    $output = (string) $renderer->renderRoot($output);
     $this->assertStringContainsString('js-view-dom-id-' . $view->dom_id, $output, 'The test view is correctly embedded.');
     $view->destroy();
 
     $view->setArguments([27]);
     $this->executeView($view);
     $output = $view->render();
-    $output = $renderer->renderRoot($output);
+    $output = (string) $renderer->renderRoot($output);
     $this->assertStringNotContainsString('John', $output, 'The test view is correctly embedded with inherited arguments.');
     $this->assertStringContainsString('George', $output, 'The test view is correctly embedded with inherited arguments.');
     $view->destroy();
diff --git a/core/modules/views/tests/src/Kernel/Handler/FieldDateTest.php b/core/modules/views/tests/src/Kernel/Handler/FieldDateTest.php
index f97a507ffbc0..69c237f26a37 100644
--- a/core/modules/views/tests/src/Kernel/Handler/FieldDateTest.php
+++ b/core/modules/views/tests/src/Kernel/Handler/FieldDateTest.php
@@ -163,7 +163,7 @@ class FieldDateTest extends ViewsKernelTestBase {
       else {
         $message = "$date_format format matches.";
       }
-      $actual_result = $view->field['created']->advancedRender($view->result[0]);
+      $actual_result = (string) $view->field['created']->advancedRender($view->result[0]);
       $this->assertEquals($expected_result, strip_tags($actual_result), $message);
     }
   }
@@ -181,7 +181,7 @@ class FieldDateTest extends ViewsKernelTestBase {
   protected function assertRenderedFutureDatesEqual(ViewExecutable $view, array $map): void {
     foreach ($map as $format => $result) {
       $view->field['destroyed']->options['date_format'] = $format;
-      $view_result = $view->field['destroyed']->advancedRender($view->result[0]);
+      $view_result = (string) $view->field['destroyed']->advancedRender($view->result[0]);
       $this->assertEquals($result, strip_tags($view_result), "$format format matches.");
     }
   }
diff --git a/core/modules/views/tests/src/Kernel/Handler/FieldFieldTest.php b/core/modules/views/tests/src/Kernel/Handler/FieldFieldTest.php
index 458cab3e06f2..995b9af0b3d2 100644
--- a/core/modules/views/tests/src/Kernel/Handler/FieldFieldTest.php
+++ b/core/modules/views/tests/src/Kernel/Handler/FieldFieldTest.php
@@ -405,41 +405,41 @@ class FieldFieldTest extends ViewsKernelTestBase {
     $this->assertEquals("1, 3", $executable->getStyle()->getField(0, 'field_test_multiple'));
     $this->assertEquals("1", $executable->getStyle()->getField(0, 'field_test_multiple_1'));
     $this->assertEquals("3", $executable->getStyle()->getField(0, 'field_test_multiple_2'));
-    $this->assertEquals($date_formatter->format($this->testUsers[0]->getCreatedTime(), 'custom', 'Y'), trim(strip_tags($executable->getStyle()->getField(0, 'created'))));
-    $this->assertEquals($date_formatter->format($this->testUsers[0]->getCreatedTime(), 'custom', 'H:i:s'), trim(strip_tags($executable->getStyle()->getField(0, 'created_1'))));
-    $this->assertEquals($date_formatter->format($this->testUsers[0]->getCreatedTime(), 'fallback'), trim(strip_tags($executable->getStyle()->getField(0, 'created_2'))));
+    $this->assertEquals($date_formatter->format($this->testUsers[0]->getCreatedTime(), 'custom', 'Y'), trim(strip_tags((string) $executable->getStyle()->getField(0, 'created'))));
+    $this->assertEquals($date_formatter->format($this->testUsers[0]->getCreatedTime(), 'custom', 'H:i:s'), trim(strip_tags((string) $executable->getStyle()->getField(0, 'created_1'))));
+    $this->assertEquals($date_formatter->format($this->testUsers[0]->getCreatedTime(), 'fallback'), trim(strip_tags((string) $executable->getStyle()->getField(0, 'created_2'))));
 
     $this->assertEquals($this->testUsers[1]->getTimeZone(), $executable->getStyle()->getField(1, 'timezone'));
     $this->assertEquals("7, 0", $executable->getStyle()->getField(1, 'field_test_multiple'));
     $this->assertEquals("7", $executable->getStyle()->getField(1, 'field_test_multiple_1'));
     $this->assertEquals("0", $executable->getStyle()->getField(1, 'field_test_multiple_2'));
-    $this->assertEquals($date_formatter->format($this->testUsers[1]->getCreatedTime(), 'custom', 'Y'), trim(strip_tags($executable->getStyle()->getField(1, 'created'))));
-    $this->assertEquals($date_formatter->format($this->testUsers[1]->getCreatedTime(), 'custom', 'H:i:s'), trim(strip_tags($executable->getStyle()->getField(1, 'created_1'))));
-    $this->assertEquals($date_formatter->format($this->testUsers[1]->getCreatedTime(), 'fallback'), trim(strip_tags($executable->getStyle()->getField(1, 'created_2'))));
+    $this->assertEquals($date_formatter->format($this->testUsers[1]->getCreatedTime(), 'custom', 'Y'), trim(strip_tags((string) $executable->getStyle()->getField(1, 'created'))));
+    $this->assertEquals($date_formatter->format($this->testUsers[1]->getCreatedTime(), 'custom', 'H:i:s'), trim(strip_tags((string) $executable->getStyle()->getField(1, 'created_1'))));
+    $this->assertEquals($date_formatter->format($this->testUsers[1]->getCreatedTime(), 'fallback'), trim(strip_tags((string) $executable->getStyle()->getField(1, 'created_2'))));
 
     $this->assertEquals($this->testUsers[2]->getTimeZone(), $executable->getStyle()->getField(2, 'timezone'));
     $this->assertEquals("3, 5", $executable->getStyle()->getField(2, 'field_test_multiple'));
     $this->assertEquals("3", $executable->getStyle()->getField(2, 'field_test_multiple_1'));
     $this->assertEquals("5", $executable->getStyle()->getField(2, 'field_test_multiple_2'));
-    $this->assertEquals($date_formatter->format($this->testUsers[2]->getCreatedTime(), 'custom', 'Y'), trim(strip_tags($executable->getStyle()->getField(2, 'created'))));
-    $this->assertEquals($date_formatter->format($this->testUsers[2]->getCreatedTime(), 'custom', 'H:i:s'), trim(strip_tags($executable->getStyle()->getField(2, 'created_1'))));
-    $this->assertEquals($date_formatter->format($this->testUsers[2]->getCreatedTime(), 'fallback'), trim(strip_tags($executable->getStyle()->getField(2, 'created_2'))));
+    $this->assertEquals($date_formatter->format($this->testUsers[2]->getCreatedTime(), 'custom', 'Y'), trim(strip_tags((string) $executable->getStyle()->getField(2, 'created'))));
+    $this->assertEquals($date_formatter->format($this->testUsers[2]->getCreatedTime(), 'custom', 'H:i:s'), trim(strip_tags((string) $executable->getStyle()->getField(2, 'created_1'))));
+    $this->assertEquals($date_formatter->format($this->testUsers[2]->getCreatedTime(), 'fallback'), trim(strip_tags((string) $executable->getStyle()->getField(2, 'created_2'))));
 
     $this->assertEquals($this->testUsers[3]->getTimeZone(), $executable->getStyle()->getField(3, 'timezone'));
     $this->assertEquals("9, 9", $executable->getStyle()->getField(3, 'field_test_multiple'));
     $this->assertEquals("9", $executable->getStyle()->getField(3, 'field_test_multiple_1'));
     $this->assertEquals("9", $executable->getStyle()->getField(3, 'field_test_multiple_2'));
-    $this->assertEquals($date_formatter->format($this->testUsers[3]->getCreatedTime(), 'custom', 'Y'), trim(strip_tags($executable->getStyle()->getField(3, 'created'))));
-    $this->assertEquals($date_formatter->format($this->testUsers[3]->getCreatedTime(), 'custom', 'H:i:s'), trim(strip_tags($executable->getStyle()->getField(3, 'created_1'))));
-    $this->assertEquals($date_formatter->format($this->testUsers[3]->getCreatedTime(), 'fallback'), trim(strip_tags($executable->getStyle()->getField(3, 'created_2'))));
+    $this->assertEquals($date_formatter->format($this->testUsers[3]->getCreatedTime(), 'custom', 'Y'), trim(strip_tags((string) $executable->getStyle()->getField(3, 'created'))));
+    $this->assertEquals($date_formatter->format($this->testUsers[3]->getCreatedTime(), 'custom', 'H:i:s'), trim(strip_tags((string) $executable->getStyle()->getField(3, 'created_1'))));
+    $this->assertEquals($date_formatter->format($this->testUsers[3]->getCreatedTime(), 'fallback'), trim(strip_tags((string) $executable->getStyle()->getField(3, 'created_2'))));
 
     $this->assertEquals($this->testUsers[4]->getTimeZone(), $executable->getStyle()->getField(4, 'timezone'));
     $this->assertEquals("9, 0", $executable->getStyle()->getField(4, 'field_test_multiple'));
     $this->assertEquals("9", $executable->getStyle()->getField(4, 'field_test_multiple_1'));
     $this->assertEquals("0", $executable->getStyle()->getField(4, 'field_test_multiple_2'));
-    $this->assertEquals($date_formatter->format($this->testUsers[4]->getCreatedTime(), 'custom', 'Y'), trim(strip_tags($executable->getStyle()->getField(4, 'created'))));
-    $this->assertEquals($date_formatter->format($this->testUsers[4]->getCreatedTime(), 'custom', 'H:i:s'), trim(strip_tags($executable->getStyle()->getField(4, 'created_1'))));
-    $this->assertEquals($date_formatter->format($this->testUsers[4]->getCreatedTime(), 'fallback'), trim(strip_tags($executable->getStyle()->getField(4, 'created_2'))));
+    $this->assertEquals($date_formatter->format($this->testUsers[4]->getCreatedTime(), 'custom', 'Y'), trim(strip_tags((string) $executable->getStyle()->getField(4, 'created'))));
+    $this->assertEquals($date_formatter->format($this->testUsers[4]->getCreatedTime(), 'custom', 'H:i:s'), trim(strip_tags((string) $executable->getStyle()->getField(4, 'created_1'))));
+    $this->assertEquals($date_formatter->format($this->testUsers[4]->getCreatedTime(), 'fallback'), trim(strip_tags((string) $executable->getStyle()->getField(4, 'created_2'))));
   }
 
   /**
diff --git a/core/modules/views/tests/src/Kernel/Handler/FieldKernelTest.php b/core/modules/views/tests/src/Kernel/Handler/FieldKernelTest.php
index 7dda16f0aca2..45c98c3d8f67 100644
--- a/core/modules/views/tests/src/Kernel/Handler/FieldKernelTest.php
+++ b/core/modules/views/tests/src/Kernel/Handler/FieldKernelTest.php
@@ -57,7 +57,7 @@ class FieldKernelTest extends ViewsKernelTestBase {
 
     $random_text = $this->randomMachineName();
     $view->field['job']->setTestValue($random_text);
-    $output = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $output = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['job']->theme($view->result[0]);
     });
     $this->assertEquals($random_text, $output, 'Make sure the render method rendered the manual set value.');
@@ -145,13 +145,13 @@ class FieldKernelTest extends ViewsKernelTestBase {
 
     // Don't check the rewrite checkbox, so the text shouldn't appear.
     $id_field->options['alter']['text'] = $random_text = $this->randomMachineName();
-    $output = $renderer->executeInRenderContext(new RenderContext(), function () use ($id_field, $row) {
+    $output = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($id_field, $row) {
       return $id_field->theme($row);
     });
     $this->assertNotSubString($output, $random_text);
 
     $id_field->options['alter']['alter_text'] = TRUE;
-    $output = $renderer->executeInRenderContext(new RenderContext(), function () use ($id_field, $row) {
+    $output = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($id_field, $row) {
       return $id_field->theme($row);
     });
     $this->assertSubString($output, $random_text);
@@ -172,7 +172,7 @@ class FieldKernelTest extends ViewsKernelTestBase {
 
     $id_field->options['alter']['text'] = '<p>{{ id }}</p>';
     $id_field->options['alter']['alter_text'] = TRUE;
-    $output = $renderer->executeInRenderContext(new RenderContext(), function () use ($id_field, $row) {
+    $output = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($id_field, $row) {
       return $id_field->theme($row);
     });
     $this->assertSubString($output, '<p>1</p>');
@@ -180,7 +180,7 @@ class FieldKernelTest extends ViewsKernelTestBase {
     // Add a non-safe HTML tag and make sure this gets removed.
     $id_field->options['alter']['text'] = '<p>{{ id }} <script>alert("Script removed")</script></p>';
     $id_field->options['alter']['alter_text'] = TRUE;
-    $output = $renderer->executeInRenderContext(new RenderContext(), function () use ($id_field, $row) {
+    $output = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($id_field, $row) {
       return $id_field->theme($row);
     });
     $this->assertSubString($output, '<p>1 alert("Script removed")</p>');
@@ -204,7 +204,7 @@ class FieldKernelTest extends ViewsKernelTestBase {
 
     $id_field->options['alter']['text'] = '<p>{{ id }}</p>';
     $id_field->options['alter']['alter_text'] = TRUE;
-    $output = $renderer->executeInRenderContext(new RenderContext(), function () use ($id_field, $row) {
+    $output = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($id_field, $row) {
       return $id_field->theme($row);
     });
     $this->assertSubString($output, '<p>1</p>');
@@ -212,7 +212,7 @@ class FieldKernelTest extends ViewsKernelTestBase {
     // Add a non-safe HTML tag and make sure this gets removed.
     $id_field->options['alter']['text'] = '<p>{{ id }} <script>alert("Script removed")</script></p>';
     $id_field->options['alter']['alter_text'] = TRUE;
-    $output = $renderer->executeInRenderContext(new RenderContext(), function () use ($id_field, $row) {
+    $output = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($id_field, $row) {
       return $id_field->theme($row);
     });
     $this->assertSubString($output, '<p>1 alert("Script removed")</p>');
@@ -235,7 +235,7 @@ class FieldKernelTest extends ViewsKernelTestBase {
     $name_field_0->options['alter']['text'] = '%1 !1';
 
     $row = $view->result[0];
-    $output = $renderer->executeInRenderContext(new RenderContext(), function () use ($name_field_0, $row) {
+    $output = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($name_field_0, $row) {
       return $name_field_0->advancedRender($row);
     });
 
@@ -248,7 +248,7 @@ class FieldKernelTest extends ViewsKernelTestBase {
     $name_field_0->options['alter']['text'] = '{{ arguments.null }} {{ raw_arguments.null }}';
 
     $row = $view->result[0];
-    $output = $renderer->executeInRenderContext(new RenderContext(), function () use ($name_field_0, $row) {
+    $output = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($name_field_0, $row) {
       return $name_field_0->advancedRender($row);
     });
 
@@ -284,17 +284,17 @@ class FieldKernelTest extends ViewsKernelTestBase {
       $expected_output_1 = "$row->views_test_data_name $row->views_test_data_name";
       $expected_output_2 = "$row->views_test_data_name $row->views_test_data_name $row->views_test_data_name";
 
-      $output = $renderer->executeInRenderContext(new RenderContext(), function () use ($name_field_0, $row) {
+      $output = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($name_field_0, $row) {
         return $name_field_0->advancedRender($row);
       });
       $this->assertEquals($expected_output_0, $output, new FormattableMarkup('Test token replacement: "@token" gave "@output"', ['@token' => $name_field_0->options['alter']['text'], '@output' => $output]));
 
-      $output = $renderer->executeInRenderContext(new RenderContext(), function () use ($name_field_1, $row) {
+      $output = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($name_field_1, $row) {
         return $name_field_1->advancedRender($row);
       });
       $this->assertEquals($expected_output_1, $output, new FormattableMarkup('Test token replacement: "@token" gave "@output"', ['@token' => $name_field_1->options['alter']['text'], '@output' => $output]));
 
-      $output = $renderer->executeInRenderContext(new RenderContext(), function () use ($name_field_2, $row) {
+      $output = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($name_field_2, $row) {
         return $name_field_2->advancedRender($row);
       });
       $this->assertEquals($expected_output_2, $output, new FormattableMarkup('Test token replacement: "@token" gave "@output"', ['@token' => $name_field_2->options['alter']['text'], '@output' => $output]));
@@ -306,7 +306,7 @@ class FieldKernelTest extends ViewsKernelTestBase {
 
     $random_text = $this->randomMachineName();
     $job_field->setTestValue($random_text);
-    $output = $renderer->executeInRenderContext(new RenderContext(), function () use ($job_field, $row) {
+    $output = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($job_field, $row) {
       return $job_field->advancedRender($row);
     });
     $this->assertSubString($output, $random_text, new FormattableMarkup('Make sure the self token (@token => @value) appears in the output (@output)', [
@@ -320,7 +320,7 @@ class FieldKernelTest extends ViewsKernelTestBase {
     $job_field->options['alter']['text'] = $old_token;
     $random_text = $this->randomMachineName();
     $job_field->setTestValue($random_text);
-    $output = $renderer->executeInRenderContext(new RenderContext(), function () use ($job_field, $row) {
+    $output = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($job_field, $row) {
       return $job_field->advancedRender($row);
     });
     $this->assertEquals($old_token, $output, new FormattableMarkup('Make sure the old token style (@token => @value) is not changed in the output (@output)', ['@value' => $random_text, '@output' => $output, '@token' => $job_field->options['alter']['text']]));
@@ -330,7 +330,7 @@ class FieldKernelTest extends ViewsKernelTestBase {
     $job_field->options['alter']['text'] = '<h1>{{ job }}</h1>';
     $random_text = $this->randomMachineName();
     $job_field->setTestValue('<span>' . $random_text . '</span>');
-    $output = $renderer->executeInRenderContext(new RenderContext(), function () use ($job_field, $row) {
+    $output = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($job_field, $row) {
       return $job_field->advancedRender($row);
     });
     $this->assertSame('<h1>&lt;span&gt;' . $random_text . '&lt;/span&gt;</h1>', (string) $output, 'Valid tags are allowed in rewrite templates and token replacements.');
@@ -340,7 +340,7 @@ class FieldKernelTest extends ViewsKernelTestBase {
     $job_field->options['alter']['text'] = $rewrite_template;
     $random_text = $this->randomMachineName();
     $job_field->setTestValue($random_text);
-    $output = $renderer->executeInRenderContext(new RenderContext(), function () use ($job_field, $row) {
+    $output = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($job_field, $row) {
       return $job_field->advancedRender($row);
     });
     $this->assertNotSubString($output, '<script>', 'Ensure a script tag in the rewrite template is removed.');
@@ -349,7 +349,7 @@ class FieldKernelTest extends ViewsKernelTestBase {
     $job_field->options['alter']['text'] = $rewrite_template;
     $random_text = $this->randomMachineName();
     $job_field->setTestValue($random_text);
-    $output = $renderer->executeInRenderContext(new RenderContext(), function () use ($job_field, $row) {
+    $output = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($job_field, $row) {
       return $job_field->advancedRender($row);
     });
     $this->assertEquals($random_text, $output, new FormattableMarkup('Make sure a script tag in the template (@template) is removed, leaving only the replaced token in the output (@output)', ['@output' => $output, '@template' => $rewrite_template]));
@@ -367,7 +367,7 @@ class FieldKernelTest extends ViewsKernelTestBase {
     $view->field['name']->options['exclude'] = TRUE;
 
     $output = $view->preview();
-    $output = $renderer->renderRoot($output);
+    $output = (string) $renderer->renderRoot($output);
     foreach ($this->dataSet() as $entry) {
       $this->assertNotSubString($output, $entry['name']);
     }
@@ -376,7 +376,7 @@ class FieldKernelTest extends ViewsKernelTestBase {
     $view->field['name']->options['exclude'] = FALSE;
 
     $output = $view->preview();
-    $output = $renderer->renderRoot($output);
+    $output = (string) $renderer->renderRoot($output);
     foreach ($this->dataSet() as $entry) {
       $this->assertSubString($output, $entry['name']);
     }
@@ -416,28 +416,28 @@ class FieldKernelTest extends ViewsKernelTestBase {
 
     // Test a valid string.
     $view->result[0]->{$column_map_reversed['name']} = $random_name;
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame($random_name, (string) $render, 'By default, a string should not be treated as empty.');
 
     // Test an empty string.
     $view->result[0]->{$column_map_reversed['name']} = "";
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame("", $render, 'By default, "" should not be treated as empty.');
 
     // Test zero as an integer.
     $view->result[0]->{$column_map_reversed['name']} = 0;
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame('0', (string) $render, 'By default, 0 should not be treated as empty.');
 
     // Test zero as a string.
     $view->result[0]->{$column_map_reversed['name']} = "0";
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame("0", (string) $render, 'By default, "0" should not be treated as empty.');
@@ -449,28 +449,28 @@ class FieldKernelTest extends ViewsKernelTestBase {
 
     // Test a valid string.
     $view->result[0]->{$column_map_reversed['name']} = $random_name;
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame($random_name, (string) $render, 'If hide_empty is checked, a string should not be treated as empty.');
 
     // Test an empty string.
     $view->result[0]->{$column_map_reversed['name']} = "";
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame("", $render, 'If hide_empty is checked, "" should be treated as empty.');
 
     // Test zero as an integer.
     $view->result[0]->{$column_map_reversed['name']} = 0;
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame('0', (string) $render, 'If hide_empty is checked, but not empty_zero, 0 should not be treated as empty.');
 
     // Test zero as a string.
     $view->result[0]->{$column_map_reversed['name']} = "0";
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame("0", (string) $render, 'If hide_empty is checked, but not empty_zero, "0" should not be treated as empty.');
@@ -482,14 +482,14 @@ class FieldKernelTest extends ViewsKernelTestBase {
 
     // Test zero as an integer.
     $view->result[0]->{$column_map_reversed['name']} = 0;
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame("", $render, 'If hide_empty and empty_zero are checked, 0 should be treated as empty.');
 
     // Test zero as a string.
     $view->result[0]->{$column_map_reversed['name']} = "0";
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame("", $render, 'If hide_empty and empty_zero are checked, "0" should be treated as empty.');
@@ -504,28 +504,28 @@ class FieldKernelTest extends ViewsKernelTestBase {
 
     // Test a valid string.
     $view->result[0]->{$column_map_reversed['name']} = $random_value;
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame($random_name, (string) $render, 'If the rewritten string is not empty, it should not be treated as empty.');
 
     // Test an empty string.
     $view->result[0]->{$column_map_reversed['name']} = "";
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame($random_name, (string) $render, 'If the rewritten string is not empty, "" should not be treated as empty.');
 
     // Test zero as an integer.
     $view->result[0]->{$column_map_reversed['name']} = 0;
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame($random_name, (string) $render, 'If the rewritten string is not empty, 0 should not be treated as empty.');
 
     // Test zero as a string.
     $view->result[0]->{$column_map_reversed['name']} = "0";
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame($random_name, (string) $render, 'If the rewritten string is not empty, "0" should not be treated as empty.');
@@ -539,28 +539,28 @@ class FieldKernelTest extends ViewsKernelTestBase {
 
     // Test a valid string.
     $view->result[0]->{$column_map_reversed['name']} = $random_name;
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame($random_name, (string) $render, 'If the rewritten string is empty, it should not be treated as empty.');
 
     // Test an empty string.
     $view->result[0]->{$column_map_reversed['name']} = "";
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame("", $render, 'If the rewritten string is empty, "" should be treated as empty.');
 
     // Test zero as an integer.
     $view->result[0]->{$column_map_reversed['name']} = 0;
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame('0', (string) $render, 'If the rewritten string is empty, 0 should not be treated as empty.');
 
     // Test zero as a string.
     $view->result[0]->{$column_map_reversed['name']} = "0";
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame("0", (string) $render, 'If the rewritten string is empty, "0" should not be treated as empty.');
@@ -575,28 +575,28 @@ class FieldKernelTest extends ViewsKernelTestBase {
 
     // Test a valid string.
     $view->result[0]->{$column_map_reversed['name']} = $random_name;
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame("0", (string) $render, 'If the rewritten string is zero and empty_zero is not checked, the string rewritten as 0 should not be treated as empty.');
 
     // Test an empty string.
     $view->result[0]->{$column_map_reversed['name']} = "";
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame("0", (string) $render, 'If the rewritten string is zero and empty_zero is not checked, "" rewritten as 0 should not be treated as empty.');
 
     // Test zero as an integer.
     $view->result[0]->{$column_map_reversed['name']} = 0;
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame("0", (string) $render, 'If the rewritten string is zero and empty_zero is not checked, 0 should not be treated as empty.');
 
     // Test zero as a string.
     $view->result[0]->{$column_map_reversed['name']} = "0";
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame("0", (string) $render, 'If the rewritten string is zero and empty_zero is not checked, "0" should not be treated as empty.');
@@ -611,28 +611,28 @@ class FieldKernelTest extends ViewsKernelTestBase {
 
     // Test a valid string.
     $view->result[0]->{$column_map_reversed['name']} = $random_name;
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame($random_value, (string) $render, 'If the original and rewritten strings are valid, it should not be treated as empty.');
 
     // Test an empty string.
     $view->result[0]->{$column_map_reversed['name']} = "";
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame("", $render, 'If either the original or rewritten string is invalid, "" should be treated as empty.');
 
     // Test zero as an integer.
     $view->result[0]->{$column_map_reversed['name']} = 0;
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame($random_value, (string) $render, 'If the original and rewritten strings are valid, 0 should not be treated as empty.');
 
     // Test zero as a string.
     $view->result[0]->{$column_map_reversed['name']} = "0";
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame($random_value, (string) $render, 'If the original and rewritten strings are valid, "0" should not be treated as empty.');
@@ -647,28 +647,28 @@ class FieldKernelTest extends ViewsKernelTestBase {
 
     // Test a valid string.
     $view->result[0]->{$column_map_reversed['name']} = $random_name;
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame("", (string) $render, 'If the rewritten string is zero, it should be treated as empty.');
 
     // Test an empty string.
     $view->result[0]->{$column_map_reversed['name']} = "";
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame("", $render, 'If the rewritten string is zero, "" should be treated as empty.');
 
     // Test zero as an integer.
     $view->result[0]->{$column_map_reversed['name']} = 0;
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame("", $render, 'If the rewritten string is zero, 0 should not be treated as empty.');
 
     // Test zero as a string.
     $view->result[0]->{$column_map_reversed['name']} = "0";
-    $render = $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
+    $render = (string) $renderer->executeInRenderContext(new RenderContext(), function () use ($view) {
       return $view->field['name']->advancedRender($view->result[0]);
     });
     $this->assertSame("", $render, 'If the rewritten string is zero, "0" should not be treated as empty.');
diff --git a/core/modules/views/tests/src/Kernel/Handler/FieldRenderedEntityTest.php b/core/modules/views/tests/src/Kernel/Handler/FieldRenderedEntityTest.php
index a1971abfd0f3..ebf8435ab26d 100644
--- a/core/modules/views/tests/src/Kernel/Handler/FieldRenderedEntityTest.php
+++ b/core/modules/views/tests/src/Kernel/Handler/FieldRenderedEntityTest.php
@@ -128,7 +128,7 @@ class FieldRenderedEntityTest extends ViewsKernelTestBase {
     $renderer = \Drupal::service('renderer');
     $renderer->renderPlain($build);
     for ($i = 1; $i <= 3; $i++) {
-      $view_field = $view->style_plugin->getField($i - 1, 'rendered_entity');
+      $view_field = (string) $view->style_plugin->getField($i - 1, 'rendered_entity');
       $search_result = str_contains($view_field, "Test $i");
       $this->assertFalse($search_result, "The text 'Test $i' not found in the view.");
     }
@@ -201,7 +201,7 @@ class FieldRenderedEntityTest extends ViewsKernelTestBase {
     $renderer = \Drupal::service('renderer');
     $renderer->renderPlain($build);
     for ($i = 1; $i <= 3; $i++) {
-      $view_field = $view->style_plugin->getField($i - 1, 'rendered_entity');
+      $view_field = (string) $view->style_plugin->getField($i - 1, 'rendered_entity');
       $search_result = str_contains($view_field, "Test $i");
       $this->assertTrue($search_result, "The text 'Test $i' found in the view.");
     }
diff --git a/core/modules/views/tests/src/Kernel/Handler/FilterCombineTest.php b/core/modules/views/tests/src/Kernel/Handler/FilterCombineTest.php
index 0d5ddaa59eaa..7acdd8f897a0 100644
--- a/core/modules/views/tests/src/Kernel/Handler/FilterCombineTest.php
+++ b/core/modules/views/tests/src/Kernel/Handler/FilterCombineTest.php
@@ -193,7 +193,7 @@ class FilterCombineTest extends ViewsKernelTestBase {
 
     // Confirm that the query with multiple filters used the "CONCAT_WS"
     // operator.
-    $this->assertStringContainsString('CONCAT_WS(', $view->query->query());
+    $this->assertStringContainsString('CONCAT_WS(', (string) $view->query->query());
   }
 
   /**
@@ -279,7 +279,7 @@ class FilterCombineTest extends ViewsKernelTestBase {
 
     // Confirm that the query with single filter does not use the "CONCAT_WS"
     // operator.
-    $this->assertStringNotContainsString('CONCAT_WS(', $view->query->query());
+    $this->assertStringNotContainsString('CONCAT_WS(', (string) $view->query->query());
   }
 
   /**
diff --git a/core/modules/views/tests/src/Kernel/Plugin/DisplayPageTest.php b/core/modules/views/tests/src/Kernel/Plugin/DisplayPageTest.php
index 86579c6cc2db..c129b5c6f437 100644
--- a/core/modules/views/tests/src/Kernel/Plugin/DisplayPageTest.php
+++ b/core/modules/views/tests/src/Kernel/Plugin/DisplayPageTest.php
@@ -177,7 +177,7 @@ class DisplayPageTest extends ViewsKernelTestBase {
     $this->setRawContent($output);
     $result = $this->xpath('//div[@class=:class]/a', [':class' => 'more-link']);
     $this->assertEquals(Url::fromRoute('view.test_display_more.page_1')->toString(), $result[0]->attributes()->href, 'The right more link is shown.');
-    $this->assertEquals($expected_more_text, trim($result[0][0]), 'The right link text is shown.');
+    $this->assertEquals($expected_more_text, trim((string) $result[0][0]), 'The right link text is shown.');
 
     // Test the renderMoreLink method directly. This could be directly unit
     // tested.
@@ -186,7 +186,7 @@ class DisplayPageTest extends ViewsKernelTestBase {
     $this->setRawContent($more_link);
     $result = $this->xpath('//div[@class=:class]/a', [':class' => 'more-link']);
     $this->assertEquals(Url::fromRoute('view.test_display_more.page_1')->toString(), $result[0]->attributes()->href, 'The right more link is shown.');
-    $this->assertEquals($expected_more_text, trim($result[0][0]), 'The right link text is shown.');
+    $this->assertEquals($expected_more_text, trim((string) $result[0][0]), 'The right link text is shown.');
 
     // Test the useMoreText method directly. This could be directly unit
     // tested.
diff --git a/core/modules/views/tests/src/Kernel/Plugin/StyleHtmlListTest.php b/core/modules/views/tests/src/Kernel/Plugin/StyleHtmlListTest.php
index e6acb31bacea..d32b951617fd 100644
--- a/core/modules/views/tests/src/Kernel/Plugin/StyleHtmlListTest.php
+++ b/core/modules/views/tests/src/Kernel/Plugin/StyleHtmlListTest.php
@@ -26,7 +26,7 @@ class StyleHtmlListTest extends ViewsKernelTestBase {
   public function testDefaultRowClasses() {
     $view = Views::getView('test_style_html_list');
     $output = $view->preview();
-    $output = \Drupal::service('renderer')->renderRoot($output);
+    $output = (string) \Drupal::service('renderer')->renderRoot($output);
 
     // Check that an empty class attribute is not added if the wrapper class is
     // not set.
@@ -41,7 +41,7 @@ class StyleHtmlListTest extends ViewsKernelTestBase {
     $view->style_plugin->options['wrapper_class'] = 'wrapper-class';
 
     $output = $view->preview();
-    $output = \Drupal::service('renderer')->renderRoot($output);
+    $output = (string) \Drupal::service('renderer')->renderRoot($output);
 
     // Check that class attribute is present if the wrapper class is set.
     $this->assertStringContainsString('<div class="wrapper-class">', $output, 'Class is added to DIV');
diff --git a/core/modules/views/tests/src/Kernel/Plugin/StyleMappingTest.php b/core/modules/views/tests/src/Kernel/Plugin/StyleMappingTest.php
index 2ffadd2bc117..de72163be33b 100644
--- a/core/modules/views/tests/src/Kernel/Plugin/StyleMappingTest.php
+++ b/core/modules/views/tests/src/Kernel/Plugin/StyleMappingTest.php
@@ -26,7 +26,7 @@ class StyleMappingTest extends StyleTestBase {
    */
   public function testMappedOutput() {
     $view = Views::getView('test_style_mapping');
-    $output = $this->mappedOutputHelper($view);
+    $output = (string) $this->mappedOutputHelper($view);
     $this->assertStringNotContainsString('job', $output, 'The job field is added to the view but not in the mapping.');
     $view->destroy();
 
@@ -47,7 +47,7 @@ class StyleMappingTest extends StyleTestBase {
    */
   protected function mappedOutputHelper(ViewExecutable $view) {
     $output = $view->preview();
-    $rendered_output = \Drupal::service('renderer')->renderRoot($output);
+    $rendered_output = (string) \Drupal::service('renderer')->renderRoot($output);
     $this->storeViewPreview($rendered_output);
     $rows = $this->elements->body->div->div;
     $data_set = $this->dataSet();
diff --git a/core/modules/views/tests/src/Kernel/Plugin/StyleTableUnitTest.php b/core/modules/views/tests/src/Kernel/Plugin/StyleTableUnitTest.php
index 4ee14e4f3747..f2afa1c49aad 100644
--- a/core/modules/views/tests/src/Kernel/Plugin/StyleTableUnitTest.php
+++ b/core/modules/views/tests/src/Kernel/Plugin/StyleTableUnitTest.php
@@ -118,7 +118,7 @@ class StyleTableUnitTest extends PluginKernelTestBase {
     $this->prepareView($view);
     $view->field['name']->options['exclude'] = TRUE;
     $output = $view->preview();
-    $output = \Drupal::service('renderer')->renderRoot($output);
+    $output = (string) \Drupal::service('renderer')->renderRoot($output);
     $this->assertStringNotContainsString('views-field-name', $output, "Excluded field's wrapper was not rendered.");
     $view->destroy();
 
@@ -126,7 +126,7 @@ class StyleTableUnitTest extends PluginKernelTestBase {
     // rendered.
     $this->executeView($view);
     $output = $view->preview();
-    $output = \Drupal::service('renderer')->renderRoot($output);
+    $output = (string) \Drupal::service('renderer')->renderRoot($output);
 
     $this->assertStringNotContainsString('custom text', $output, 'Empty handler was not rendered on a non empty table.');
 
@@ -135,7 +135,7 @@ class StyleTableUnitTest extends PluginKernelTestBase {
     $view->executed = TRUE;
     $view->result = [];
     $output = $view->preview();
-    $output = \Drupal::service('renderer')->renderRoot($output);
+    $output = (string) \Drupal::service('renderer')->renderRoot($output);
 
     $this->assertStringContainsString('custom text', $output, 'Empty handler got rendered on an empty table.');
   }
diff --git a/core/modules/views/tests/src/Kernel/Plugin/StyleTest.php b/core/modules/views/tests/src/Kernel/Plugin/StyleTest.php
index 864b99c06c1d..3ec96c45e8de 100644
--- a/core/modules/views/tests/src/Kernel/Plugin/StyleTest.php
+++ b/core/modules/views/tests/src/Kernel/Plugin/StyleTest.php
@@ -286,7 +286,7 @@ class StyleTest extends ViewsKernelTestBase {
     $view->style_plugin->options['row_class'] = $random_name . " test-token-{{ name }}";
 
     $output = $view->preview();
-    $html_dom = $this->getHtmlDom($this->container->get('renderer')->renderRoot($output));
+    $html_dom = $this->getHtmlDom((string) $this->container->get('renderer')->renderRoot($output));
 
     $rows = $html_dom->body->div->div;
     $count = 0;
diff --git a/core/modules/views/tests/src/Kernel/ViewExecutableTest.php b/core/modules/views/tests/src/Kernel/ViewExecutableTest.php
index 77a8d4a5de8c..963b300d845e 100644
--- a/core/modules/views/tests/src/Kernel/ViewExecutableTest.php
+++ b/core/modules/views/tests/src/Kernel/ViewExecutableTest.php
@@ -445,7 +445,7 @@ class ViewExecutableTest extends ViewsKernelTestBase {
     $count = 0;
     foreach ($view->displayHandlers as $id => $display) {
       $match = function ($value) use ($display) {
-        return str_contains($value, $display->display['display_title']);
+        return str_contains((string) $value, $display->display['display_title']);
       };
       $this->assertNotEmpty(array_filter($validate[$id], $match), "Error message found for $id display");
       $count++;
diff --git a/core/tests/Drupal/KernelTests/Core/Asset/AttachedAssetsTest.php b/core/tests/Drupal/KernelTests/Core/Asset/AttachedAssetsTest.php
index 008ae210994b..72adf818c0d2 100644
--- a/core/tests/Drupal/KernelTests/Core/Asset/AttachedAssetsTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Asset/AttachedAssetsTest.php
@@ -93,8 +93,8 @@ class AttachedAssetsTest extends KernelTestBase {
 
     $css_render_array = \Drupal::service('asset.css.collection_renderer')->render($css);
     $js_render_array = \Drupal::service('asset.js.collection_renderer')->render($js);
-    $rendered_css = $this->renderer->renderPlain($css_render_array);
-    $rendered_js = $this->renderer->renderPlain($js_render_array);
+    $rendered_css = (string) $this->renderer->renderPlain($css_render_array);
+    $rendered_js = (string) $this->renderer->renderPlain($js_render_array);
     $query_string = $this->container->get('asset.query_string')->get();
     $this->assertStringContainsString('<link rel="stylesheet" media="all" href="' . $this->fileUrlGenerator->generateString('core/modules/system/tests/modules/common_test/bar.css') . '?' . $query_string . '" />', $rendered_css, 'Rendering an external CSS file.');
     $this->assertStringContainsString('<script src="' . $this->fileUrlGenerator->generateString('core/modules/system/tests/modules/common_test/foo.js') . '?' . $query_string . '"></script>', $rendered_js, 'Rendering an external JavaScript file.');
@@ -133,8 +133,8 @@ class AttachedAssetsTest extends KernelTestBase {
 
     $css_render_array = \Drupal::service('asset.css.collection_renderer')->render($css);
     $js_render_array = \Drupal::service('asset.js.collection_renderer')->render($js);
-    $rendered_css = $this->renderer->renderPlain($css_render_array);
-    $rendered_js = $this->renderer->renderPlain($js_render_array);
+    $rendered_css = (string) $this->renderer->renderPlain($css_render_array);
+    $rendered_js = (string) $this->renderer->renderPlain($js_render_array);
     $this->assertStringContainsString('<link rel="stylesheet" media="all" href="http://example.com/stylesheet.css" />', $rendered_css, 'Rendering an external CSS file.');
     $this->assertStringContainsString('<script src="http://example.com/script.js"></script>', $rendered_js, 'Rendering an external JavaScript file.');
   }
@@ -148,7 +148,7 @@ class AttachedAssetsTest extends KernelTestBase {
 
     $js = $this->assetResolver->getJsAssets($assets, FALSE, \Drupal::languageManager()->getCurrentLanguage())[1];
     $js_render_array = \Drupal::service('asset.js.collection_renderer')->render($js);
-    $rendered_js = $this->renderer->renderPlain($js_render_array);
+    $rendered_js = (string) $this->renderer->renderPlain($js_render_array);
     $expected_1 = '<script src="http://example.com/deferred-external.js" foo="bar" defer></script>';
     $expected_2 = '<script src="' . $this->fileUrlGenerator->generateString('core/modules/system/tests/modules/common_test/deferred-internal.js') . '?v=1" defer bar="foo"></script>';
     $this->assertStringContainsString($expected_1, $rendered_js, 'Rendered external JavaScript with correct defer and random attributes.');
@@ -164,7 +164,7 @@ class AttachedAssetsTest extends KernelTestBase {
 
     $js = $this->assetResolver->getJsAssets($assets, TRUE, \Drupal::languageManager()->getCurrentLanguage())[1];
     $js_render_array = \Drupal::service('asset.js.collection_renderer')->render($js);
-    $rendered_js = $this->renderer->renderPlain($js_render_array);
+    $rendered_js = (string) $this->renderer->renderPlain($js_render_array);
     $expected_1 = '<script src="http://example.com/deferred-external.js" foo="bar" defer></script>';
     $expected_2 = '<script src="' . $this->fileUrlGenerator->generateString('core/modules/system/tests/modules/common_test/deferred-internal.js') . '?v=1" defer bar="foo"></script>';
     $this->assertStringContainsString($expected_1, $rendered_js, 'Rendered external JavaScript with correct defer and random attributes.');
@@ -238,7 +238,7 @@ class AttachedAssetsTest extends KernelTestBase {
 
     $js = $this->assetResolver->getJsAssets($assets, FALSE, \Drupal::languageManager()->getCurrentLanguage())[0];
     $js_render_array = \Drupal::service('asset.js.collection_renderer')->render($js);
-    $rendered_js = $this->renderer->renderPlain($js_render_array);
+    $rendered_js = (string) $this->renderer->renderPlain($js_render_array);
     $query_string = $this->container->get('asset.query_string')->get();
     $this->assertStringContainsString('<script src="' . $this->fileUrlGenerator->generateString('core/modules/system/tests/modules/common_test/header.js') . '?' . $query_string . '"></script>', $rendered_js, 'The JS asset in common_test/js-header appears in the header.');
     $this->assertStringContainsString('<script src="' . $this->fileUrlGenerator->generateString('core/misc/drupal.js'), $rendered_js, 'The JS asset of the direct dependency (core/drupal) of common_test/js-header appears in the header.');
@@ -266,7 +266,7 @@ class AttachedAssetsTest extends KernelTestBase {
     $js = $this->assetResolver->getJsAssets($assets, FALSE, \Drupal::languageManager()->getCurrentLanguage())[1];
     $js_render_array = \Drupal::service('asset.js.collection_renderer')->render($js);
 
-    $rendered_js = $this->renderer->renderPlain($js_render_array);
+    $rendered_js = (string) $this->renderer->renderPlain($js_render_array);
     $this->assertStringContainsString('core/assets/vendor/once/once.min.js?v=1.0.1', $rendered_js, 'JavaScript version identifiers correctly appended to URLs');
   }
 
@@ -295,7 +295,7 @@ class AttachedAssetsTest extends KernelTestBase {
     // Retrieve the rendered JavaScript and test against the regex.
     $js = $this->assetResolver->getJsAssets($assets, FALSE, \Drupal::languageManager()->getCurrentLanguage())[1];
     $js_render_array = \Drupal::service('asset.js.collection_renderer')->render($js);
-    $rendered_js = $this->renderer->renderPlain($js_render_array);
+    $rendered_js = (string) $this->renderer->renderPlain($js_render_array);
     $matches = [];
     if (preg_match_all('/weight_([-0-9]+_[0-9]+)/', $rendered_js, $matches)) {
       $result = $matches[1];
@@ -337,7 +337,7 @@ class AttachedAssetsTest extends KernelTestBase {
     // Retrieve the rendered CSS and test against the regex.
     $css = $this->assetResolver->getCssAssets($assets, FALSE, \Drupal::languageManager()->getCurrentLanguage());
     $css_render_array = \Drupal::service('asset.css.collection_renderer')->render($css);
-    $rendered_css = $this->renderer->renderPlain($css_render_array);
+    $rendered_css = (string) $this->renderer->renderPlain($css_render_array);
     $matches = [];
     if (preg_match_all('/([a-z]+)_weight_([-0-9]+_[0-9]+)/', $rendered_css, $matches)) {
       $result = $matches[0];
@@ -360,7 +360,7 @@ class AttachedAssetsTest extends KernelTestBase {
 
     $js = $this->assetResolver->getJsAssets($assets, FALSE, \Drupal::languageManager()->getCurrentLanguage())[1];
     $js_render_array = \Drupal::service('asset.js.collection_renderer')->render($js);
-    $rendered_js = $this->renderer->renderPlain($js_render_array);
+    $rendered_js = (string) $this->renderer->renderPlain($js_render_array);
     // Verify that lighter CSS assets are rendered first.
     $this->assertLessThan(strpos($rendered_js, 'first.js'), strpos($rendered_js, 'lighter.css'));
     // Verify that lighter JavaScript assets are rendered first.
@@ -385,7 +385,7 @@ class AttachedAssetsTest extends KernelTestBase {
     // takes place.
     $js = $this->assetResolver->getJsAssets($assets, FALSE, \Drupal::languageManager()->getCurrentLanguage())[1];
     $js_render_array = \Drupal::service('asset.js.collection_renderer')->render($js);
-    $rendered_js = $this->renderer->renderPlain($js_render_array);
+    $rendered_js = (string) $this->renderer->renderPlain($js_render_array);
     // Verify that JavaScript weight is correctly altered by the alter hook.
     $this->assertLessThan(strpos($rendered_js, 'core/misc/tableselect.js'), strpos($rendered_js, 'alter.js'));
   }
@@ -407,7 +407,7 @@ class AttachedAssetsTest extends KernelTestBase {
     $assets = AttachedAssets::createFromRenderArray($build);
     $js = $this->assetResolver->getJsAssets($assets, FALSE, \Drupal::languageManager()->getCurrentLanguage())[1];
     $js_render_array = \Drupal::service('asset.js.collection_renderer')->render($js);
-    $rendered_js = $this->renderer->renderPlain($js_render_array);
+    $rendered_js = (string) $this->renderer->renderPlain($js_render_array);
     $this->assertStringContainsString('core/assets/vendor/jquery-form/jquery.form.min.js', (string) $rendered_js, 'Altered library dependencies are added to the page.');
   }
 
@@ -456,9 +456,9 @@ class AttachedAssetsTest extends KernelTestBase {
     $this->assertArrayHasKey('core/modules/system/tests/modules/common_test/querystring.js?arg1=value1&arg2=value2', $js);
 
     $css_render_array = \Drupal::service('asset.css.collection_renderer')->render($css);
-    $rendered_css = $this->renderer->renderPlain($css_render_array);
+    $rendered_css = (string) $this->renderer->renderPlain($css_render_array);
     $js_render_array = \Drupal::service('asset.js.collection_renderer')->render($js);
-    $rendered_js = $this->renderer->renderPlain($js_render_array);
+    $rendered_js = (string) $this->renderer->renderPlain($js_render_array);
     $query_string = $this->container->get('asset.query_string')->get();
     $this->assertStringContainsString('<link rel="stylesheet" media="all" href="' . str_replace('&', '&amp;', $this->fileUrlGenerator->generateString('core/modules/system/tests/modules/common_test/querystring.css?arg1=value1&arg2=value2')) . '&amp;' . $query_string . '" />', $rendered_css, 'CSS file with query string gets version query string correctly appended..');
     $this->assertStringContainsString('<script src="' . str_replace('&', '&amp;', $this->fileUrlGenerator->generateString('core/modules/system/tests/modules/common_test/querystring.js?arg1=value1&arg2=value2')) . '&amp;' . $query_string . '"></script>', $rendered_js, 'JavaScript file with query string gets version query string correctly appended.');
diff --git a/core/tests/Drupal/KernelTests/Core/Entity/EntityAccessControlHandlerTest.php b/core/tests/Drupal/KernelTests/Core/Entity/EntityAccessControlHandlerTest.php
index ccbc1ef101bf..3a34d85990d1 100644
--- a/core/tests/Drupal/KernelTests/Core/Entity/EntityAccessControlHandlerTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Entity/EntityAccessControlHandlerTest.php
@@ -48,7 +48,7 @@ class EntityAccessControlHandlerTest extends EntityLanguageTestBase {
         '@op' => $op,
       ]);
 
-      $this->assertEquals($object->access($op, $account), $result, $message);
+      $this->assertEquals($object->access($op, $account), $result, (string) $message);
     }
   }
 
diff --git a/core/tests/Drupal/KernelTests/Core/Entity/EntityDecoupledTranslationRevisionsTest.php b/core/tests/Drupal/KernelTests/Core/Entity/EntityDecoupledTranslationRevisionsTest.php
index 5541ec27c411..bcd9955e6cae 100644
--- a/core/tests/Drupal/KernelTests/Core/Entity/EntityDecoupledTranslationRevisionsTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Entity/EntityDecoupledTranslationRevisionsTest.php
@@ -294,7 +294,7 @@ class EntityDecoupledTranslationRevisionsTest extends EntityKernelTestBase {
       $this->stepIndex = $index;
       $revision_id = call_user_func_array([$this, 'doEditStep'], $step);
     }
-    return $revision_id;
+    return (int) $revision_id;
   }
 
   /**
diff --git a/core/tests/Drupal/KernelTests/Core/Entity/EntityDefinitionUpdateTest.php b/core/tests/Drupal/KernelTests/Core/Entity/EntityDefinitionUpdateTest.php
index a293e1a2399b..48b33b75512e 100644
--- a/core/tests/Drupal/KernelTests/Core/Entity/EntityDefinitionUpdateTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Entity/EntityDefinitionUpdateTest.php
@@ -278,7 +278,7 @@ class EntityDefinitionUpdateTest extends EntityKernelTestBase {
     $this->assertTrue($this->entityDefinitionUpdateManager->needsUpdates(), 'EntityDefinitionUpdateManager reports that updates are needed.');
     $changes = $this->entityDefinitionUpdateManager->getChangeSummary();
     $this->assertCount(1, $changes['entity_test_update']);
-    $this->assertEquals('The A new base field field needs to be installed.', strip_tags($changes['entity_test_update'][0]));
+    $this->assertEquals('The A new base field field needs to be installed.', strip_tags((string) $changes['entity_test_update'][0]));
     $this->applyEntityUpdates();
     $this->assertTrue($this->database->schema()->fieldExists('entity_test_update', 'new_base_field'), 'Column created in shared table for new_base_field.');
 
@@ -288,7 +288,7 @@ class EntityDefinitionUpdateTest extends EntityKernelTestBase {
     $this->assertTrue($this->entityDefinitionUpdateManager->needsUpdates(), 'EntityDefinitionUpdateManager reports that updates are needed.');
     $changes = $this->entityDefinitionUpdateManager->getChangeSummary();
     $this->assertCount(1, $changes['entity_test_update']);
-    $this->assertEquals('The A new base field field needs to be updated.', strip_tags($changes['entity_test_update'][0]));
+    $this->assertEquals('The A new base field field needs to be updated.', strip_tags((string) $changes['entity_test_update'][0]));
     $this->applyEntityUpdates();
     $this->assertTrue($this->database->schema()->indexExists('entity_test_update', 'entity_test_update_field__new_base_field'), 'Index created.');
 
@@ -298,7 +298,7 @@ class EntityDefinitionUpdateTest extends EntityKernelTestBase {
     $this->assertTrue($this->entityDefinitionUpdateManager->needsUpdates(), 'EntityDefinitionUpdateManager reports that updates are needed.');
     $changes = $this->entityDefinitionUpdateManager->getChangeSummary();
     $this->assertCount(1, $changes['entity_test_update']);
-    $this->assertEquals('The A new base field field needs to be updated.', strip_tags($changes['entity_test_update'][0]));
+    $this->assertEquals('The A new base field field needs to be updated.', strip_tags((string) $changes['entity_test_update'][0]));
     $this->applyEntityUpdates();
     $this->assertFalse($this->database->schema()->indexExists('entity_test_update', 'entity_test_update_field__new_base_field'), 'Index deleted.');
 
@@ -309,7 +309,7 @@ class EntityDefinitionUpdateTest extends EntityKernelTestBase {
     $this->assertTrue($this->entityDefinitionUpdateManager->needsUpdates(), 'EntityDefinitionUpdateManager reports that updates are needed.');
     $changes = $this->entityDefinitionUpdateManager->getChangeSummary();
     $this->assertCount(1, $changes['entity_test_update']);
-    $this->assertEquals('The A new base field field needs to be updated.', strip_tags($changes['entity_test_update'][0]));
+    $this->assertEquals('The A new base field field needs to be updated.', strip_tags((string) $changes['entity_test_update'][0]));
     $this->applyEntityUpdates();
     $this->assertFalse($this->database->schema()->fieldExists('entity_test_update', 'new_base_field'), 'Original column deleted in shared table for new_base_field.');
     $this->assertTrue($this->database->schema()->fieldExists('entity_test_update', 'new_base_field__value'), 'Value column created in shared table for new_base_field.');
@@ -321,7 +321,7 @@ class EntityDefinitionUpdateTest extends EntityKernelTestBase {
     $this->assertTrue($this->entityDefinitionUpdateManager->needsUpdates(), 'EntityDefinitionUpdateManager reports that updates are needed.');
     $changes = $this->entityDefinitionUpdateManager->getChangeSummary();
     $this->assertCount(1, $changes['entity_test_update']);
-    $this->assertEquals('The A new base field field needs to be uninstalled.', strip_tags($changes['entity_test_update'][0]));
+    $this->assertEquals('The A new base field field needs to be uninstalled.', strip_tags((string) $changes['entity_test_update'][0]));
     $this->applyEntityUpdates();
     $this->assertFalse($this->database->schema()->fieldExists('entity_test_update', 'new_base_field_value'), 'Value column deleted from shared table for new_base_field.');
     $this->assertFalse($this->database->schema()->fieldExists('entity_test_update', 'new_base_field_format'), 'Format column deleted from shared table for new_base_field.');
@@ -338,7 +338,7 @@ class EntityDefinitionUpdateTest extends EntityKernelTestBase {
     $this->addBaseField('string', 'entity_test_update', FALSE, FALSE);
     $changes = $this->entityDefinitionUpdateManager->getChangeSummary();
     $this->assertCount(1, $changes['entity_test_update']);
-    $this->assertEquals('The new_base_field field needs to be installed.', strip_tags($changes['entity_test_update'][0]));
+    $this->assertEquals('The new_base_field field needs to be installed.', strip_tags((string) $changes['entity_test_update'][0]));
     $this->applyEntityUpdates();
 
     // Add an index on the base field, ensure the update manager reports it with
@@ -346,7 +346,7 @@ class EntityDefinitionUpdateTest extends EntityKernelTestBase {
     $this->addBaseFieldIndex();
     $changes = $this->entityDefinitionUpdateManager->getChangeSummary();
     $this->assertCount(1, $changes['entity_test_update']);
-    $this->assertEquals('The new_base_field field needs to be updated.', strip_tags($changes['entity_test_update'][0]));
+    $this->assertEquals('The new_base_field field needs to be updated.', strip_tags((string) $changes['entity_test_update'][0]));
     $this->applyEntityUpdates();
 
     // Remove the base field, ensure the update manager reports it with the
@@ -354,7 +354,7 @@ class EntityDefinitionUpdateTest extends EntityKernelTestBase {
     $this->removeBaseField();
     $changes = $this->entityDefinitionUpdateManager->getChangeSummary();
     $this->assertCount(1, $changes['entity_test_update']);
-    $this->assertEquals('The new_base_field field needs to be uninstalled.', strip_tags($changes['entity_test_update'][0]));
+    $this->assertEquals('The new_base_field field needs to be uninstalled.', strip_tags((string) $changes['entity_test_update'][0]));
   }
 
   /**
@@ -367,7 +367,7 @@ class EntityDefinitionUpdateTest extends EntityKernelTestBase {
     $this->assertTrue($this->entityDefinitionUpdateManager->needsUpdates(), 'EntityDefinitionUpdateManager reports that updates are needed.');
     $changes = $this->entityDefinitionUpdateManager->getChangeSummary();
     $this->assertCount(1, $changes['entity_test_update']);
-    $this->assertEquals('The A new bundle field field needs to be installed.', strip_tags($changes['entity_test_update'][0]));
+    $this->assertEquals('The A new bundle field field needs to be installed.', strip_tags((string) $changes['entity_test_update'][0]));
     $this->applyEntityUpdates();
     $this->assertTrue($this->database->schema()->tableExists('entity_test_update__new_bundle_field'), 'Dedicated table created for new_bundle_field.');
 
@@ -378,7 +378,7 @@ class EntityDefinitionUpdateTest extends EntityKernelTestBase {
     $this->assertTrue($this->entityDefinitionUpdateManager->needsUpdates(), 'EntityDefinitionUpdateManager reports that updates are needed.');
     $changes = $this->entityDefinitionUpdateManager->getChangeSummary();
     $this->assertCount(1, $changes['entity_test_update']);
-    $this->assertEquals('The A new bundle field field needs to be updated.', strip_tags($changes['entity_test_update'][0]));
+    $this->assertEquals('The A new bundle field field needs to be updated.', strip_tags((string) $changes['entity_test_update'][0]));
     $this->applyEntityUpdates();
     $this->assertTrue($this->database->schema()->fieldExists('entity_test_update__new_bundle_field', 'new_bundle_field_format'), 'Format column created in dedicated table for new_base_field.');
 
@@ -388,7 +388,7 @@ class EntityDefinitionUpdateTest extends EntityKernelTestBase {
     $this->assertTrue($this->entityDefinitionUpdateManager->needsUpdates(), 'EntityDefinitionUpdateManager reports that updates are needed.');
     $changes = $this->entityDefinitionUpdateManager->getChangeSummary();
     $this->assertCount(1, $changes['entity_test_update']);
-    $this->assertEquals('The A new bundle field field needs to be uninstalled.', strip_tags($changes['entity_test_update'][0]));
+    $this->assertEquals('The A new bundle field field needs to be uninstalled.', strip_tags((string) $changes['entity_test_update'][0]));
     $this->applyEntityUpdates();
     $this->assertFalse($this->database->schema()->tableExists('entity_test_update__new_bundle_field'), 'Dedicated table deleted for new_bundle_field.');
   }
diff --git a/core/tests/Drupal/KernelTests/Core/Entity/RevisionableContentEntityBaseTest.php b/core/tests/Drupal/KernelTests/Core/Entity/RevisionableContentEntityBaseTest.php
index b0ce3373d0b0..dee4b5cbc3ec 100644
--- a/core/tests/Drupal/KernelTests/Core/Entity/RevisionableContentEntityBaseTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Entity/RevisionableContentEntityBaseTest.php
@@ -53,7 +53,7 @@ class RevisionableContentEntityBaseTest extends EntityKernelTestBase {
 
     // Create the second revision.
     $entity->setNewRevision(TRUE);
-    $random_timestamp = rand(1e8, 2e8);
+    $random_timestamp = rand(100_000_000, 200_000_000);
     $this->createRevision($entity, $user, $random_timestamp, 'This is my log message');
 
     $revision_id = $entity->getRevisionId();
@@ -68,14 +68,14 @@ class RevisionableContentEntityBaseTest extends EntityKernelTestBase {
     $this->assertEquals('This is my log message', $entity->getRevisionLogMessage());
 
     // Create the third revision.
-    $random_timestamp = rand(1e8, 2e8);
+    $random_timestamp = rand(100_000_000, 200_000_000);
     $this->createRevision($entity, $user, $random_timestamp, 'This is my log message');
     $this->assertItemsTableCount(3, $definition);
     $revision_ids[] = $entity->getRevisionId();
 
     // Create another 3 revisions.
     foreach (range(1, 3) as $count) {
-      $timestamp = rand(1e8, 2e8);
+      $timestamp = rand(100_000_000, 200_000_000);
       $this->createRevision($entity, $user, $timestamp, 'This is my log message number: ' . $count);
       $revision_ids[] = $entity->getRevisionId();
     }
diff --git a/core/tests/Drupal/KernelTests/Core/File/StreamWrapperTest.php b/core/tests/Drupal/KernelTests/Core/File/StreamWrapperTest.php
index 5a3a59290bb9..d0a88403a6f2 100644
--- a/core/tests/Drupal/KernelTests/Core/File/StreamWrapperTest.php
+++ b/core/tests/Drupal/KernelTests/Core/File/StreamWrapperTest.php
@@ -120,8 +120,8 @@ class StreamWrapperTest extends FileTestBase {
     $this->assertNotFalse($handle, 'Able to open a file for appending, reading and writing.');
 
     // Attempt to change options on the file stream: should all fail.
-    $this->assertFalse(@stream_set_blocking($handle, 0), 'Unable to set to non blocking using a local stream wrapper.');
-    $this->assertFalse(@stream_set_blocking($handle, 1), 'Unable to set to blocking using a local stream wrapper.');
+    $this->assertFalse(@stream_set_blocking($handle, FALSE), 'Unable to set to non blocking using a local stream wrapper.');
+    $this->assertFalse(@stream_set_blocking($handle, TRUE), 'Unable to set to blocking using a local stream wrapper.');
     $this->assertFalse(@stream_set_timeout($handle, 1), 'Unable to set read time out using a local stream wrapper.');
     $this->assertEquals(-1 /*EOF*/, @stream_set_write_buffer($handle, 512), 'Unable to set write buffer using a local stream wrapper.');
 
diff --git a/core/tests/Drupal/KernelTests/Core/Menu/MenuTreeStorageTest.php b/core/tests/Drupal/KernelTests/Core/Menu/MenuTreeStorageTest.php
index 0704cec75d24..b06eacfe638f 100644
--- a/core/tests/Drupal/KernelTests/Core/Menu/MenuTreeStorageTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Menu/MenuTreeStorageTest.php
@@ -435,7 +435,7 @@ class MenuTreeStorageTest extends KernelTestBase {
     $found_parents = $query->execute()->fetchAllKeyed(0, 1);
 
     $this->assertSameSize($parents, $found_parents, 'Found expected number of parents');
-    $this->assertCount($raw['depth'], $found_parents, 'Number of parents is the same as the depth');
+    $this->assertCount((int) $raw['depth'], $found_parents, 'Number of parents is the same as the depth');
 
     $materialized_path = $this->treeStorage->getRootPathIds($id);
     $this->assertEquals(array_values($parents), array_values($materialized_path), 'Parents match the materialized path');
diff --git a/core/tests/Drupal/KernelTests/Core/Render/Element/RenderElementTypesTest.php b/core/tests/Drupal/KernelTests/Core/Render/Element/RenderElementTypesTest.php
index d2f36d7b733d..6eb81c3a7f9b 100644
--- a/core/tests/Drupal/KernelTests/Core/Render/Element/RenderElementTypesTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Render/Element/RenderElementTypesTest.php
@@ -185,7 +185,7 @@ class RenderElementTypesTest extends KernelTestBase {
     ];
 
     foreach ($elements as $element) {
-      $xml = new \SimpleXMLElement(\Drupal::service('renderer')->renderRoot($element['value']));
+      $xml = new \SimpleXMLElement((string) \Drupal::service('renderer')->renderRoot($element['value']));
       $result = $xml->xpath($element['expected']);
       $this->assertNotEmpty($result, '"' . $element['name'] . '" input rendered correctly.');
     }
@@ -216,7 +216,7 @@ class RenderElementTypesTest extends KernelTestBase {
     ];
 
     foreach ($elements as $element) {
-      $xml = new \SimpleXMLElement(\Drupal::service('renderer')->renderRoot($element['value']));
+      $xml = new \SimpleXMLElement((string) \Drupal::service('renderer')->renderRoot($element['value']));
       $result = $xml->xpath($element['expected']);
       $this->assertNotEmpty($result, '"' . $element['name'] . '" is rendered correctly.');
     }
@@ -232,7 +232,7 @@ class RenderElementTypesTest extends KernelTestBase {
       'expected' => '//div[@class="compact-link"]/a[contains(@href, "admin/compact?") and text()="Show descriptions"]',
     ];
 
-    $xml = new \SimpleXMLElement(\Drupal::service('renderer')->renderRoot($element['value']));
+    $xml = new \SimpleXMLElement((string) \Drupal::service('renderer')->renderRoot($element['value']));
     $result = $xml->xpath($element['expected']);
     $this->assertNotEmpty($result, '"' . $element['name'] . '" is rendered correctly.');
   }