diff --git a/core/modules/simpletest/src/RandomGeneratorTrait.php b/core/modules/simpletest/src/RandomGeneratorTrait.php
index 2d8b635..be7fa0e 100644
--- a/core/modules/simpletest/src/RandomGeneratorTrait.php
+++ b/core/modules/simpletest/src/RandomGeneratorTrait.php
@@ -6,6 +6,11 @@
 
 /**
  * Provides random generator utility methods.
+ *
+ * @deprecated in Drupal 8.0.0, will be removed before Drupal 9.0.0.
+ * The trait was moved to another namespace.
+ *
+ * @see \Drupal\Tests
  */
 trait RandomGeneratorTrait {
 
diff --git a/core/modules/simpletest/src/SessionTestTrait.php b/core/modules/simpletest/src/SessionTestTrait.php
index 042956e..f041614 100644
--- a/core/modules/simpletest/src/SessionTestTrait.php
+++ b/core/modules/simpletest/src/SessionTestTrait.php
@@ -6,6 +6,11 @@
 
 /**
  * Provides methods to generate and get session name in tests.
+ *
+ * @deprecated in Drupal 8.0.0 will be removed before 9.0.0.
+ * This was moved to another namespace.
+ *
+ * @see \Drupal\Tests
  */
 trait SessionTestTrait {
 
diff --git a/core/modules/simpletest/src/TestBase.php b/core/modules/simpletest/src/TestBase.php
index 03d308d..54223f5 100644
--- a/core/modules/simpletest/src/TestBase.php
+++ b/core/modules/simpletest/src/TestBase.php
@@ -2,6 +2,7 @@
 
 namespace Drupal\simpletest;
 
+use Behat\Mink\Session;
 use Drupal\Component\Render\MarkupInterface;
 use Drupal\Component\Utility\Crypt;
 use Drupal\Component\Utility\SafeMarkup;
@@ -13,6 +14,8 @@
 use Drupal\Core\Site\Settings;
 use Drupal\Core\StreamWrapper\PublicStream;
 use Drupal\Core\Utility\Error;
+use Drupal\Tests\RandomGeneratorTrait;
+use Drupal\Tests\SessionTestTrait;
 
 /**
  * Base class for Drupal tests.
diff --git a/core/modules/simpletest/src/WebAssert.php b/core/modules/simpletest/src/WebAssert.php
index 063473b..56f4465 100644
--- a/core/modules/simpletest/src/WebAssert.php
+++ b/core/modules/simpletest/src/WebAssert.php
@@ -8,6 +8,11 @@
 
 /**
  * Defines a class with methods for asserting presence of elements during tests.
+ *
+ * @deprecated in Drupal 8.0.0 will be removed before 9.0.0.
+ * This was moved to another namespace.
+ *
+ * @see \Drupal\Tests
  */
 class WebAssert extends MinkWebAssert {
 
diff --git a/core/tests/Drupal/KernelTests/KernelTestBase.php b/core/tests/Drupal/KernelTests/KernelTestBase.php
index dffe81d..7e50430 100644
--- a/core/tests/Drupal/KernelTests/KernelTestBase.php
+++ b/core/tests/Drupal/KernelTests/KernelTestBase.php
@@ -19,7 +19,7 @@
 use Drupal\Core\Site\Settings;
 use Drupal\simpletest\AssertContentTrait;
 use Drupal\simpletest\AssertHelperTrait;
-use Drupal\simpletest\RandomGeneratorTrait;
+use Drupal\Tests\RandomGeneratorTrait;
 use Drupal\simpletest\TestServiceProvider;
 use Symfony\Component\DependencyInjection\Reference;
 use Symfony\Component\HttpFoundation\Request;
diff --git a/core/tests/Drupal/Tests/BrowserTestBase.php b/core/tests/Drupal/Tests/BrowserTestBase.php
index 8d8ea2b..d194257 100644
--- a/core/tests/Drupal/Tests/BrowserTestBase.php
+++ b/core/tests/Drupal/Tests/BrowserTestBase.php
@@ -20,9 +20,9 @@
 use Drupal\Core\StreamWrapper\StreamWrapperInterface;
 use Drupal\Core\Test\TestRunnerKernel;
 use Drupal\Core\Url;
-use Drupal\simpletest\RandomGeneratorTrait;
-use Drupal\simpletest\SessionTestTrait;
-use Drupal\simpletest\WebAssert;
+use Drupal\Tests\RandomGeneratorTrait;
+use Drupal\Tests\SessionTestTrait;
+use Drupal\Tests\WebAssert as WebAssertClass;
 use Drupal\user\Entity\Role;
 use Drupal\user\Entity\User;
 use Drupal\user\UserInterface;
@@ -39,11 +39,6 @@
  * @ingroup testing
  */
 abstract class BrowserTestBase extends \PHPUnit_Framework_TestCase {
-
-  /**
-   * @todo Move these into Drupal\Tests namespace and leave deprecated stubs
-   *   in simpletest module. See https://www.drupal.org/node/2702281
-   */
   use RandomGeneratorTrait;
   use SessionTestTrait;
 
@@ -534,11 +529,11 @@ public function getSession($name = NULL) {
    * @param string $name
    *   (optional) Name of the session. Defaults to the active session.
    *
-   * @return \Drupal\simpletest\WebAssert
+   * @return \Drupal\Tests\WebAssert
    *   A new web-assert option for asserting the presence of elements with.
    */
   public function assertSession($name = NULL) {
-    return new WebAssert($this->getSession($name));
+    return new WebAssertClass($this->getSession($name));
   }
 
   /**
diff --git a/core/modules/simpletest/src/RandomGeneratorTrait.php b/core/tests/Drupal/Tests/RandomGeneratorTrait.php
similarity index 99%
copy from core/modules/simpletest/src/RandomGeneratorTrait.php
copy to core/tests/Drupal/Tests/RandomGeneratorTrait.php
index 2d8b635..4fdd89a 100644
--- a/core/modules/simpletest/src/RandomGeneratorTrait.php
+++ b/core/tests/Drupal/Tests/RandomGeneratorTrait.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace Drupal\simpletest;
+namespace Drupal\Tests;
 
 use Drupal\Component\Utility\Random;
 
diff --git a/core/modules/simpletest/src/SessionTestTrait.php b/core/tests/Drupal/Tests/SessionTestTrait.php
similarity index 96%
copy from core/modules/simpletest/src/SessionTestTrait.php
copy to core/tests/Drupal/Tests/SessionTestTrait.php
index 042956e..e71fdf2 100644
--- a/core/modules/simpletest/src/SessionTestTrait.php
+++ b/core/tests/Drupal/Tests/SessionTestTrait.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace Drupal\simpletest;
+namespace Drupal\Tests;
 
 use Symfony\Component\HttpFoundation\Request;
 
diff --git a/core/modules/simpletest/src/WebAssert.php b/core/tests/Drupal/Tests/WebAssert.php
similarity index 98%
copy from core/modules/simpletest/src/WebAssert.php
copy to core/tests/Drupal/Tests/WebAssert.php
index 063473b..d863de2 100644
--- a/core/modules/simpletest/src/WebAssert.php
+++ b/core/tests/Drupal/Tests/WebAssert.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace Drupal\simpletest;
+namespace Drupal\Tests;
 
 use Behat\Mink\WebAssert as MinkWebAssert;
 use Behat\Mink\Element\TraversableElement;