diff --git a/core/modules/system/lib/Drupal/system/Tests/Session/UserImpersonatingUserTest.php b/core/modules/system/lib/Drupal/system/Tests/Session/UserImpersonatingUserTest.php
index 1aa319e..757f5bb 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Session/UserImpersonatingUserTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Session/UserImpersonatingUserTest.php
@@ -5,7 +5,7 @@
  * Contains Drupal\user\Tests\UserImpersonatingUserTest.
  */
 
-namespace Drupal\user\Tests;
+namespace Drupal\system\Tests\Session;
 
 use Drupal\Core\Session\AnonymousUserSession;
 use Drupal\Core\Session\UserSession;
@@ -29,10 +29,10 @@ function setUp() {
   }
 
   function testUserImpersonateUser() {
-    $user = \Drupal::currentUser();
+    $user = $this->container->get('current_user');
     $original_user = clone $user;
 
-    // If not currently logged in, use user_user_impersonate_user() to switch to
+    // If not currently logged in, use AccountProxy::impersonateAccount() to switch to
     // user 1. If logged in, switch to the anonymous user instead.
     if ($user->isAnonymous()) {
       $user->impersonateAccount(new UserSession(array('uid' => 1)));
@@ -43,7 +43,10 @@ function testUserImpersonateUser() {
     // Verify that the active user has changed, and that session saving is
     // disabled.
     $this->assertEqual($user->id(), ($original_user->id() == 0 ? 1 : 0), t('User switched'));
-    $this->assertFalse(\Drupal::service('session_manager')->isEnabled(), t('Session saving is disabled.'));
+    $this->assertFalse($this->container->get('session_manager')->isEnabled(), t('Session saving is disabled.'));
+
+    // Enable session saving for the purpose of this test.
+    $this->container->get('session_manager')->enable();
 
     // Perform a second (nested) impersonation.
     $user->impersonateAccount(new UserSession(array('uid' => 2)));
@@ -56,7 +59,7 @@ function testUserImpersonateUser() {
     // Since we are still impersonating the user from the first attempt,
     // session handling still needs to be disabled.
     $this->assertEqual($user->id(), ($original_user->id() == 0 ? 1 : 0), t('User switched.'));
-    $this->assertFalse(\Drupal::service('session_manager')->isEnabled(), t('Session saving is disabled.'));
+    $this->assertFalse($this->container->get('session_manager')->isEnabled(), t('Session saving is disabled.'));
 
     // Revert to the original user which was active before the first
     // impersonation attempt.
@@ -65,11 +68,25 @@ function testUserImpersonateUser() {
     // Assert that the original user is the active user again, and that session
     // saving has been re-enabled.
     $this->assertEqual($user->id(), $original_user->id(), t('Original user successfully restored.'));
+    $this->assertTrue($this->container->get('session_manager')->isEnabled(), t('Session saving is enabled.'));
 
-    // Simpletest uses user_impersonate_user() too, revert the impersonation by
-    // Simpletest to enable session saving again. This is safe because calling
-    // user_revert_user() too often simply results in returning the active user.
-    $user->revertAccount();
-    $this->assertTrue(\Drupal::service('session_manager')->isEnabled(), t('Session saving is enabled.'));
+    // Verify that AccountProxy::revertAccount and AccountProxy::revertAll()
+    // will throw exceptions if there is none left in the stack.
+    try {
+      $ex1 = new \RuntimeException();
+      $user->revertAccount();
+    }
+    catch (\RuntimeException $e) {
+      $ex1 = $e;
+    }
+    $this->assertEqual($ex1->getMessage(), t('No more account impersonations to revert.'), t('Revert account throws exception if called without previous impersonation.'));
+    try {
+      $ex2 = new \RuntimeException();
+      $user->revertAll();
+    }
+    catch (\RuntimeException $e) {
+      $ex2 = $e;
+    }
+    $this->assertEqual($ex2->getMessage(), t('No more account impersonations to revert.'), t('Revert all throws exception if called without previous impersonation.'));
   }
 }