diff --git a/core/modules/system/tests/modules/early_rendering_controller_test/src/EarlyRenderingTestController.php b/core/modules/system/tests/modules/early_rendering_controller_test/src/EarlyRenderingTestController.php
index 0b0cdf4..43d5ee5 100644
--- a/core/modules/system/tests/modules/early_rendering_controller_test/src/EarlyRenderingTestController.php
+++ b/core/modules/system/tests/modules/early_rendering_controller_test/src/EarlyRenderingTestController.php
@@ -17,7 +17,7 @@
  * see that test for documentation.
  *
  * @see core/modules/early_rendering_controller_test/early_rendering_controller_test.routing.yml
- * @see \Drupal\system\Tests\Common\EarlyRenderingControllerTest::testEarlyRendering()
+ * @see \Drupal\Tests\system\Functional\Common\EarlyRenderingControllerTest::testEarlyRendering()
  */
 class EarlyRenderingTestController extends ControllerBase {
 
diff --git a/core/modules/system/src/Tests/Common/AddFeedTest.php b/core/modules/system/tests/src/Functional/Common/AddFeedTest.php
similarity index 96%
rename from core/modules/system/src/Tests/Common/AddFeedTest.php
rename to core/modules/system/tests/src/Functional/Common/AddFeedTest.php
index 40ff215..be2ea2e 100644
--- a/core/modules/system/src/Tests/Common/AddFeedTest.php
+++ b/core/modules/system/tests/src/Functional/Common/AddFeedTest.php
@@ -1,16 +1,16 @@
 <?php
 
-namespace Drupal\system\Tests\Common;
+namespace Drupal\Tests\system\Functional\Common;
 
 use Drupal\Core\Url;
-use Drupal\simpletest\WebTestBase;
+use Drupal\Tests\BrowserTestBase;
 
 /**
  * Make sure that attaching feeds works correctly with various constructs.
  *
  * @group Common
  */
-class AddFeedTest extends WebTestBase {
+class AddFeedTest extends BrowserTestBase {
 
   /**
    * Tests attaching feeds with paths, URLs, and titles.
diff --git a/core/modules/system/src/Tests/Common/AlterTest.php b/core/modules/system/tests/src/Functional/Common/AlterTest.php
similarity index 95%
rename from core/modules/system/src/Tests/Common/AlterTest.php
rename to core/modules/system/tests/src/Functional/Common/AlterTest.php
index 863bd54..e529e9d 100644
--- a/core/modules/system/src/Tests/Common/AlterTest.php
+++ b/core/modules/system/tests/src/Functional/Common/AlterTest.php
@@ -1,15 +1,15 @@
 <?php
 
-namespace Drupal\system\Tests\Common;
+namespace Drupal\Tests\system\Functional\Common;
 
-use Drupal\simpletest\WebTestBase;
+use Drupal\Tests\BrowserTestBase;
 
 /**
  * Tests alteration of arguments passed to \Drupal::moduleHandler->alter().
  *
  * @group Common
  */
-class AlterTest extends WebTestBase {
+class AlterTest extends BrowserTestBase {
 
   /**
    * Modules to enable.
diff --git a/core/modules/system/src/Tests/Common/EarlyRenderingControllerTest.php b/core/modules/system/tests/src/Functional/Common/EarlyRenderingControllerTest.php
similarity index 97%
rename from core/modules/system/src/Tests/Common/EarlyRenderingControllerTest.php
rename to core/modules/system/tests/src/Functional/Common/EarlyRenderingControllerTest.php
index 1afdd4e..c3d1bb9 100644
--- a/core/modules/system/src/Tests/Common/EarlyRenderingControllerTest.php
+++ b/core/modules/system/tests/src/Functional/Common/EarlyRenderingControllerTest.php
@@ -1,16 +1,16 @@
 <?php
 
-namespace Drupal\system\Tests\Common;
+namespace Drupal\Tests\system\Functional\Common;
 
 use Drupal\Core\Url;
-use Drupal\simpletest\WebTestBase;
+use Drupal\Tests\BrowserTestBase;
 
 /**
  * Verifies that bubbleable metadata of early rendering is not lost.
  *
  * @group Common
  */
-class EarlyRenderingControllerTest extends WebTestBase {
+class EarlyRenderingControllerTest extends BrowserTestBase {
 
   /**
    * {@inheritdoc}
diff --git a/core/modules/system/src/Tests/Common/FormatDateTest.php b/core/modules/system/tests/src/Functional/Common/FormatDateTest.php
similarity index 94%
rename from core/modules/system/src/Tests/Common/FormatDateTest.php
rename to core/modules/system/tests/src/Functional/Common/FormatDateTest.php
index c174e34..540b846 100644
--- a/core/modules/system/src/Tests/Common/FormatDateTest.php
+++ b/core/modules/system/tests/src/Functional/Common/FormatDateTest.php
@@ -1,16 +1,16 @@
 <?php
 
-namespace Drupal\system\Tests\Common;
+namespace Drupal\Tests\system\Functional\Common;
 
 use Drupal\language\Entity\ConfigurableLanguage;
-use Drupal\simpletest\WebTestBase;
+use Drupal\Tests\BrowserTestBase;
 
 /**
  * Tests the format_date() function.
  *
  * @group Common
  */
-class FormatDateTest extends WebTestBase {
+class FormatDateTest extends BrowserTestBase {
 
   /**
    * Modules to enable.
diff --git a/core/modules/system/src/Tests/Common/NoJavaScriptAnonymousTest.php b/core/modules/system/tests/src/Functional/Common/NoJavaScriptAnonymousTest.php
similarity index 92%
rename from core/modules/system/src/Tests/Common/NoJavaScriptAnonymousTest.php
rename to core/modules/system/tests/src/Functional/Common/NoJavaScriptAnonymousTest.php
index e671f87..2be4d79 100644
--- a/core/modules/system/src/Tests/Common/NoJavaScriptAnonymousTest.php
+++ b/core/modules/system/tests/src/Functional/Common/NoJavaScriptAnonymousTest.php
@@ -1,9 +1,9 @@
 <?php
 
-namespace Drupal\system\Tests\Common;
+namespace Drupal\Tests\system\Functional\Common;
 
-use Drupal\simpletest\WebTestBase;
 use Drupal\node\NodeInterface;
+use Drupal\Tests\BrowserTestBase;
 
 /**
  * Tests that anonymous users are not served any JavaScript in the Standard
@@ -11,7 +11,7 @@
  *
  * @group Common
  */
-class NoJavaScriptAnonymousTest extends WebTestBase {
+class NoJavaScriptAnonymousTest extends BrowserTestBase {
 
   protected $profile = 'standard';
 
diff --git a/core/modules/system/src/Tests/Common/RenderWebTest.php b/core/modules/system/tests/src/Functional/Common/RenderWebTest.php
similarity index 97%
rename from core/modules/system/src/Tests/Common/RenderWebTest.php
rename to core/modules/system/tests/src/Functional/Common/RenderWebTest.php
index ed0e086..6b21305 100644
--- a/core/modules/system/src/Tests/Common/RenderWebTest.php
+++ b/core/modules/system/tests/src/Functional/Common/RenderWebTest.php
@@ -1,18 +1,18 @@
 <?php
 
-namespace Drupal\system\Tests\Common;
+namespace Drupal\Tests\system\Functional\Common;
 
 use Drupal\Component\Serialization\Json;
 use Drupal\Core\EventSubscriber\MainContentViewSubscriber;
 use Drupal\Core\Url;
-use Drupal\simpletest\WebTestBase;
+use Drupal\Tests\BrowserTestBase;
 
 /**
  * Performs integration tests on drupal_render().
  *
  * @group Common
  */
-class RenderWebTest extends WebTestBase {
+class RenderWebTest extends BrowserTestBase {
 
   /**
    * Modules to enable.
diff --git a/core/modules/system/src/Tests/Common/SimpleTestErrorCollectorTest.php b/core/modules/system/tests/src/Functional/Common/SimpleTestErrorCollectorTest.php
similarity index 87%
rename from core/modules/system/src/Tests/Common/SimpleTestErrorCollectorTest.php
rename to core/modules/system/tests/src/Functional/Common/SimpleTestErrorCollectorTest.php
index 9af773b..b59dbbf 100644
--- a/core/modules/system/src/Tests/Common/SimpleTestErrorCollectorTest.php
+++ b/core/modules/system/tests/src/Functional/Common/SimpleTestErrorCollectorTest.php
@@ -1,15 +1,15 @@
 <?php
 
-namespace Drupal\system\Tests\Common;
+namespace Drupal\Tests\system\Functional\Common;
 
-use Drupal\simpletest\WebTestBase;
+use Drupal\Tests\BrowserTestBase;
 
 /**
  * Tests SimpleTest error and exception collector.
  *
  * @group Common
  */
-class SimpleTestErrorCollectorTest extends WebTestBase {
+class SimpleTestErrorCollectorTest extends BrowserTestBase {
 
   /**
    * Modules to enable.
@@ -44,7 +44,13 @@ public function testErrorCollect() {
     else {
       // Give back the errors to the log report.
       foreach ($this->collectedErrors as $error) {
-        parent::error($error['message'], $error['group'], $error['caller']);
+        if ($error['group'] == 'User notice') {
+          // Since 'User notice' is set by trigger_error() which is used for debug
+          // set the message to a status of 'debug'.
+          $this->assert('debug', $error['message']);
+        }
+
+        $this->assert('exception', $error['message']);
       }
     }
   }
@@ -67,7 +73,7 @@ protected function error($message = '', $group = 'Other', array $caller = NULL)
     // 'User notice' group bubble up to the parent classes to be handled (and
     // eventually displayed) as normal.
     if ($group == 'User notice') {
-      parent::error($message, $group, $caller);
+      $this->assert('debug', $message);
     }
     // Everything else should be collected but not propagated.
     else {
diff --git a/core/modules/system/src/Tests/Common/UrlTest.php b/core/modules/system/tests/src/Functional/Common/UrlTest.php
similarity index 99%
rename from core/modules/system/src/Tests/Common/UrlTest.php
rename to core/modules/system/tests/src/Functional/Common/UrlTest.php
index d72f8e5..c4bdc69 100644
--- a/core/modules/system/src/Tests/Common/UrlTest.php
+++ b/core/modules/system/tests/src/Functional/Common/UrlTest.php
@@ -1,13 +1,13 @@
 <?php
 
-namespace Drupal\system\Tests\Common;
+namespace Drupal\Tests\system\Functional\Common;
 
 use Drupal\Component\Utility\UrlHelper;
 use Drupal\Core\Cache\Cache;
 use Drupal\Core\Language\Language;
 use Drupal\Core\Render\RenderContext;
 use Drupal\Core\Url;
-use Drupal\simpletest\WebTestBase;
+use Drupal\Tests\BrowserTestBase;
 
 /**
  * Confirm that \Drupal\Core\Url,
@@ -18,7 +18,7 @@
  *
  * @group Common
  */
-class UrlTest extends WebTestBase {
+class UrlTest extends BrowserTestBase {
 
   public static $modules = ['common_test', 'url_alter_test'];