diff --git a/core/modules/system/tests/src/Kernel/Mail/MailTest.php b/core/modules/system/tests/src/Kernel/Mail/MailTest.php
index f8b9a39..ddf2577 100644
--- a/core/modules/system/tests/src/Kernel/Mail/MailTest.php
+++ b/core/modules/system/tests/src/Kernel/Mail/MailTest.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace Drupal\Tests\system\Functional\Mail;
+namespace Drupal\Tests\system\Kernel\Mail;
 
 use Drupal\Component\Utility\Random;
 use Drupal\Component\Utility\Unicode;
@@ -9,20 +9,18 @@
 use Drupal\Core\Render\Markup;
 use Drupal\Core\Url;
 use Drupal\file\Entity\File;
-use Drupal\Tests\BrowserTestBase;
 use Drupal\system_mail_failure_test\Plugin\Mail\TestPhpMailFailure;
+use Drupal\Tests\token\Kernel\KernelTestBase;
 
 /**
  * Performs tests on the pluggable mailing framework.
  *
  * @group Mail
  */
-class MailTest extends BrowserTestBase {
+class MailTest extends KernelTestBase {
 
   /**
-   * Modules to enable.
-   *
-   * @var array
+   * {@inheritdoc}
    */
   public static $modules = [
     'system_mail_failure_test',
@@ -33,6 +31,15 @@ class MailTest extends BrowserTestBase {
   ];
 
   /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+    $this->installEntitySchema('file');
+    $this->installSchema('system', 'mail');
+  }
+
+  /**
    * Assert that the pluggable mail system is functional.
    */
   public function testPluggableFramework() {
@@ -44,7 +51,7 @@ public function testPluggableFramework() {
 
     // Assert whether the default mail backend is an instance of the expected
     // class.
-    $this->assertTrue($mail_backend instanceof TestPhpMailFailure, 'Default mail interface can be swapped.');
+    $this->assertInstanceOf(TestPhpMailFailure::class, $mail_backend, 'Default mail interface can be swapped.');
 
     // Add a module-specific mail backend.
     $this->config('system.mail')->set('interface.mymodule_testkey', 'test_mail_collector')->save();
@@ -54,7 +61,7 @@ public function testPluggableFramework() {
 
     // Assert whether the added mail backend is an instance of the expected
     // class.
-    $this->assertTrue($mail_backend instanceof TestMailCollector, 'Additional mail interfaces can be added.');
+    $this->assertInstanceOf(TestMailCollector::class, $mail_backend, 'Additional mail interfaces can be added.');
   }
 
   /**
@@ -98,8 +105,8 @@ public function testFromAndReplyToHeader() {
     // and default sender email.
     $captured_emails = \Drupal::state()->get('system.test_mail_collector');
     $sent_message = end($captured_emails);
-    $this->assertEqual($from_email, $sent_message['headers']['From'], 'Message is sent from the site email account.');
-    $this->assertEqual($reply_email, $sent_message['headers']['Reply-to'], 'Message reply-to headers are set.');
+    $this->assertEquals($from_email, $sent_message['headers']['From'], 'Message is sent from the site email account.');
+    $this->assertEquals($reply_email, $sent_message['headers']['Reply-to'], 'Message reply-to headers are set.');
     $this->assertFalse(isset($sent_message['headers']['Errors-To']), 'Errors-to header must not be set, it is deprecated.');
 
     // Test that long site names containing characters that need MIME encoding