diff --git a/core/modules/comment/tests/src/Kernel/CommentDefaultFormatterCacheTagsTest.php b/core/modules/comment/tests/src/Kernel/CommentDefaultFormatterCacheTagsTest.php
index bdea71df15..a0cf08c2b0 100644
--- a/core/modules/comment/tests/src/Kernel/CommentDefaultFormatterCacheTagsTest.php
+++ b/core/modules/comment/tests/src/Kernel/CommentDefaultFormatterCacheTagsTest.php
@@ -34,6 +34,10 @@ class CommentDefaultFormatterCacheTagsTest extends EntityKernelTestBase {
   protected function setUp() {
     parent::setUp();
 
+    // Prevent 'user/1' access mode.
+    // @todo Remove when https://www.drupal.org/node/540008.
+    $this->createUser(['uid' => 1, 'name' => 'user1'])->save();
+
     $session = new Session();
 
     $request = Request::create('/');
@@ -128,7 +132,7 @@ public function testCacheTags() {
       'comment:' . $comment->id(),
       'config:filter.format.plain_text',
       'user_view',
-      'user:2',
+      'user:' . $user->id(),
       'config:core.entity_form_display.comment.comment.default',
       'config:field.field.comment.comment.comment_body',
       'config:field.field.entity_test.entity_test.comment',
diff --git a/core/modules/comment/tests/src/Kernel/Views/CommentAdminViewTest.php b/core/modules/comment/tests/src/Kernel/Views/CommentAdminViewTest.php
index 86e8949905..54db9f627d 100644
--- a/core/modules/comment/tests/src/Kernel/Views/CommentAdminViewTest.php
+++ b/core/modules/comment/tests/src/Kernel/Views/CommentAdminViewTest.php
@@ -54,6 +54,10 @@ protected function setUp($import_test_views = TRUE) {
     // Create the anonymous role.
     $this->installConfig(['user']);
 
+    // Prevent 'user/1' access mode.
+    // @todo Remove when https://www.drupal.org/node/540008.
+    User::create(['uid' => 1, 'name' => 'user1'])->save();
+
     // Enable another language.
     ConfigurableLanguage::createFromLangcode('ur')->save();
     // Rebuild the container to update the default language container variable.
diff --git a/core/modules/comment/tests/src/Kernel/Views/CommentViewsKernelTestBase.php b/core/modules/comment/tests/src/Kernel/Views/CommentViewsKernelTestBase.php
index 516750382c..9c837c10ff 100644
--- a/core/modules/comment/tests/src/Kernel/Views/CommentViewsKernelTestBase.php
+++ b/core/modules/comment/tests/src/Kernel/Views/CommentViewsKernelTestBase.php
@@ -61,6 +61,10 @@ protected function setUp($import_test_views = TRUE) {
       ])
       ->save();
 
+    // Prevent 'user/1' access mode.
+    // @todo Remove when https://www.drupal.org/node/540008.
+    $this->userStorage->create(['uid' => 1, 'name' => 'user1'])->save();
+
     $admin_role = Role::create(['id' => 'admin']);
     $admin_role->grantPermission('administer comments');
     $admin_role->save();
diff --git a/core/modules/file/tests/src/Kernel/FileManagedUnitTestBase.php b/core/modules/file/tests/src/Kernel/FileManagedUnitTestBase.php
index 7c43e9bfd0..e6652a21e6 100644
--- a/core/modules/file/tests/src/Kernel/FileManagedUnitTestBase.php
+++ b/core/modules/file/tests/src/Kernel/FileManagedUnitTestBase.php
@@ -30,9 +30,13 @@ protected function setUp() {
     $this->installEntitySchema('user');
     $this->installSchema('file', ['file_usage']);
 
+    // Prevent 'user/1' access mode.
+    // @todo Remove when https://www.drupal.org/node/540008.
+    User::create(['uid' => 1, 'name' => 'user1'])->save();
+
     // Make sure that a user with uid 1 exists, self::createFile() relies on
     // it.
-    $user = User::create(['uid' => 1, 'name' => $this->randomMachineName()]);
+    $user = User::create(['uid' => 2, 'name' => $this->randomMachineName()]);
     $user->enforceIsNew();
     $user->save();
     \Drupal::currentUser()->setAccount($user);
@@ -161,9 +165,10 @@ public function assertSameFile(FileInterface $file1, FileInterface $file2) {
   public function createFile($filepath = NULL, $contents = NULL, $scheme = NULL) {
     // Don't count hook invocations caused by creating the file.
     \Drupal::state()->set('file_test.count_hook_invocations', FALSE);
+    // @todo Revert uid/1 after https://www.drupal.org/node/540008.
     $file = File::create([
       'uri' => $this->createUri($filepath, $contents, $scheme),
-      'uid' => 1,
+      'uid' => 2,
     ]);
     $file->save();
     // Write the record directly rather than using the API so we don't invoke
diff --git a/core/modules/filter/tests/src/Kernel/TextFormatElementFormTest.php b/core/modules/filter/tests/src/Kernel/TextFormatElementFormTest.php
index 8fca62e965..35b39d0bf7 100644
--- a/core/modules/filter/tests/src/Kernel/TextFormatElementFormTest.php
+++ b/core/modules/filter/tests/src/Kernel/TextFormatElementFormTest.php
@@ -38,6 +38,11 @@ protected function setUp() {
     $this->installEntitySchema('user');
     $this->installSchema('system', ['sequences']);
     $this->installConfig(['filter', 'filter_test']);
+
+    // Prevent 'user/1' access mode.
+    // @todo Remove when https://www.drupal.org/node/540008.
+    User::create(['uid' => 1, 'name' => 'user1'])->save();
+
     // Filter tips link to the full-page.
     \Drupal::service('router.builder')->rebuild();
     /* @var \Drupal\Core\Render\ElementInfoManager $manager */
diff --git a/core/modules/views/tests/src/Kernel/Handler/FieldFieldAccessTestBase.php b/core/modules/views/tests/src/Kernel/Handler/FieldFieldAccessTestBase.php
index 5ff77bc9f4..1690faaa5e 100644
--- a/core/modules/views/tests/src/Kernel/Handler/FieldFieldAccessTestBase.php
+++ b/core/modules/views/tests/src/Kernel/Handler/FieldFieldAccessTestBase.php
@@ -40,6 +40,10 @@ protected function setUp($import_test_views = TRUE) {
 
     $this->installEntitySchema('user');
 
+    // Prevent 'user/1' access mode.
+    // @todo Remove when https://www.drupal.org/node/540008.
+    User::create(['uid' => 1, 'name' => 'user1'])->save();
+
     $role_with_access = Role::create([
       'id' => 'with_access',
       'permissions' => ['view test entity field'],
diff --git a/core/modules/views/tests/src/Kernel/Handler/FieldRenderedEntityTest.php b/core/modules/views/tests/src/Kernel/Handler/FieldRenderedEntityTest.php
index 02419f4847..a7239425d9 100644
--- a/core/modules/views/tests/src/Kernel/Handler/FieldRenderedEntityTest.php
+++ b/core/modules/views/tests/src/Kernel/Handler/FieldRenderedEntityTest.php
@@ -48,6 +48,10 @@ protected function setUpFixtures() {
     $this->installEntitySchema('entity_test');
     $this->installConfig(['entity_test']);
 
+    // Prevent 'user/1' access mode.
+    // @todo Remove when https://www.drupal.org/node/540008.
+    User::create(['uid' => 1, 'name' => 'user1'])->save();
+
     EntityViewMode::create([
       'id' => 'entity_test.foobar',
       'targetEntityType' => 'entity_test',
diff --git a/core/tests/Drupal/KernelTests/Core/Entity/Element/EntityAutocompleteElementFormTest.php b/core/tests/Drupal/KernelTests/Core/Entity/Element/EntityAutocompleteElementFormTest.php
index c18910e21d..9c8a396dc0 100644
--- a/core/tests/Drupal/KernelTests/Core/Entity/Element/EntityAutocompleteElementFormTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Entity/Element/EntityAutocompleteElementFormTest.php
@@ -50,6 +50,10 @@ protected function setUp() {
     $this->installEntitySchema('entity_test_string_id');
     \Drupal::service('router.builder')->rebuild();
 
+    // Prevent 'user/1' access mode.
+    // @todo Remove when https://www.drupal.org/node/540008.
+    User::create(['uid' => 1, 'name' => 'user1'])->save();
+
     $this->testUser = User::create([
       'name' => 'foobar1',
       'mail' => 'foobar1@example.com',