diff --git a/core/lib/Drupal/Core/Cache/MemoryBackend.php b/core/lib/Drupal/Core/Cache/MemoryBackend.php
index d9bad8d..5c7f928 100644
--- a/core/lib/Drupal/Core/Cache/MemoryBackend.php
+++ b/core/lib/Drupal/Core/Cache/MemoryBackend.php
@@ -217,4 +217,13 @@ public function __sleep() {
     return [];
   }
 
+  /**
+   * Reset statically cached variables.
+   *
+   * This is only used by tests.
+   */
+  public function reset() {
+    $this->cache = [];
+  }
+
 }
diff --git a/core/modules/user/src/Tests/UserPermissionsTest.php b/core/modules/user/src/Tests/UserPermissionsTest.php
index 19dd429..e5baa49 100644
--- a/core/modules/user/src/Tests/UserPermissionsTest.php
+++ b/core/modules/user/src/Tests/UserPermissionsTest.php
@@ -7,7 +7,6 @@
 
 namespace Drupal\user\Tests;
 
-use Drupal\Core\Cache\Cache;
 use Drupal\simpletest\WebTestBase;
 use Drupal\user\RoleInterface;
 use Drupal\user\Entity\Role;
@@ -57,7 +56,6 @@ function testUserPermissionChanges() {
     // Create an additional role and mark it as admin role.
     Role::create(['is_admin' => TRUE, 'id' => 'administrator', 'label' => 'Administrator'])->save();
     $storage->resetCache();
-    Cache::invalidateTags(["config:user.role.$this->rid"]);
 
     $this->drupalLogin($this->adminUser);
     $rid = $this->rid;
@@ -72,7 +70,6 @@ function testUserPermissionChanges() {
     $this->drupalPostForm('admin/people/permissions', $edit, t('Save permissions'));
     $this->assertText(t('The changes have been saved.'), 'Successful save message displayed.');
     $storage->resetCache();
-    Cache::invalidateTags(["config:user.role.$this->rid"]);
     $this->assertTrue($account->hasPermission('administer users'), 'User now has "administer users" permission.');
     $current_permissions_hash = $permissions_hash_generator->generate($account);
     $this->assertIdentical($current_permissions_hash, $permissions_hash_generator->generate($this->loggedInUser));
@@ -86,7 +83,6 @@ function testUserPermissionChanges() {
     $this->drupalPostForm('admin/people/permissions', $edit, t('Save permissions'));
     $this->assertText(t('The changes have been saved.'), 'Successful save message displayed.');
     $storage->resetCache();
-    Cache::invalidateTags(["config:user.role.$this->rid"]);
     $this->assertFalse($account->hasPermission('access user profiles'), 'User no longer has "access user profiles" permission.');
     $current_permissions_hash = $permissions_hash_generator->generate($account);
     $this->assertIdentical($current_permissions_hash, $permissions_hash_generator->generate($this->loggedInUser));