diff --git a/core/modules/simpletest/src/BlockCreationTrait.php b/core/modules/block/tests/src/Traits/BlockCreationTrait.php
similarity index 98%
copy from core/modules/simpletest/src/BlockCreationTrait.php
copy to core/modules/block/tests/src/Traits/BlockCreationTrait.php
index b252d9e9e6..fe0a379aff 100644
--- a/core/modules/simpletest/src/BlockCreationTrait.php
+++ b/core/modules/block/tests/src/Traits/BlockCreationTrait.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace Drupal\simpletest;
+namespace Drupal\Tests\block\Traits;
 
 use Drupal\block\Entity\Block;
 
diff --git a/core/modules/simpletest/src/ContentTypeCreationTrait.php b/core/modules/node/tests/src/Traits/ContentTypeCreationTrait.php
similarity index 97%
copy from core/modules/simpletest/src/ContentTypeCreationTrait.php
copy to core/modules/node/tests/src/Traits/ContentTypeCreationTrait.php
index ec15b9af77..e633dad353 100644
--- a/core/modules/simpletest/src/ContentTypeCreationTrait.php
+++ b/core/modules/node/tests/src/Traits/ContentTypeCreationTrait.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace Drupal\simpletest;
+namespace Drupal\Tests\node\Traits;
 
 use Drupal\Component\Render\FormattableMarkup;
 use Drupal\node\Entity\NodeType;
diff --git a/core/modules/simpletest/src/NodeCreationTrait.php b/core/modules/node/tests/src/Traits/NodeCreationTrait.php
similarity index 98%
copy from core/modules/simpletest/src/NodeCreationTrait.php
copy to core/modules/node/tests/src/Traits/NodeCreationTrait.php
index 20dc3f8379..56d6fa5f5e 100644
--- a/core/modules/simpletest/src/NodeCreationTrait.php
+++ b/core/modules/node/tests/src/Traits/NodeCreationTrait.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace Drupal\simpletest;
+namespace Drupal\Tests\node\Traits;
 
 use Drupal\node\Entity\Node;
 
diff --git a/core/modules/simpletest/src/AssertHelperTrait.php b/core/modules/simpletest/src/AssertHelperTrait.php
index 5325e8c9b0..8a7ec9925b 100644
--- a/core/modules/simpletest/src/AssertHelperTrait.php
+++ b/core/modules/simpletest/src/AssertHelperTrait.php
@@ -2,34 +2,18 @@
 
 namespace Drupal\simpletest;
 
-use Drupal\Component\Render\MarkupInterface;
+use Drupal\Tests\AssertHelperTrait as BaseAssertHelperTrait;
 
 /**
  * Provides helper methods for assertions.
+ *
+ * @deprecated in Drupal 8.4.x. Will be removed before Drupal 9.0.0. Use
+ *   Drupal\Tests\AssertHelperTrait instead.
+ *
+ * @see https://www.drupal.org/node/2884454
  */
 trait AssertHelperTrait {
 
-  /**
-   * Casts MarkupInterface objects into strings.
-   *
-   * @param string|array $value
-   *   The value to act on.
-   *
-   * @return mixed
-   *   The input value, with MarkupInterface objects casted to string.
-   */
-  protected static function castSafeStrings($value) {
-    if ($value instanceof MarkupInterface) {
-      $value = (string) $value;
-    }
-    if (is_array($value)) {
-      array_walk_recursive($value, function (&$item) {
-        if ($item instanceof MarkupInterface) {
-          $item = (string) $item;
-        }
-      });
-    }
-    return $value;
-  }
+  use BaseAssertHelperTrait;
 
 }
diff --git a/core/modules/simpletest/src/BlockCreationTrait.php b/core/modules/simpletest/src/BlockCreationTrait.php
index b252d9e9e6..f5dcffe46e 100644
--- a/core/modules/simpletest/src/BlockCreationTrait.php
+++ b/core/modules/simpletest/src/BlockCreationTrait.php
@@ -2,66 +2,20 @@
 
 namespace Drupal\simpletest;
 
-use Drupal\block\Entity\Block;
+use Drupal\Tests\block\Traits\BlockCreationTrait as BaseBlockCreationTrait;
 
 /**
  * Provides methods to create and place block with default settings.
  *
  * This trait is meant to be used only by test classes.
+ *
+ * @deprecated in Drupal 8.4.x. Will be removed before Drupal 9.0.0. Use
+ *   Drupal\Tests\AssertHelperTrait instead.
+ *
+ * @see https://www.drupal.org/node/2884454
  */
 trait BlockCreationTrait {
 
-  /**
-   * Creates a block instance based on default settings.
-   *
-   * @param string $plugin_id
-   *   The plugin ID of the block type for this block instance.
-   * @param array $settings
-   *   (optional) An associative array of settings for the block entity.
-   *   Override the defaults by specifying the key and value in the array, for
-   *   example:
-   *   @code
-   *     $this->drupalPlaceBlock('system_powered_by_block', array(
-   *       'label' => t('Hello, world!'),
-   *     ));
-   *   @endcode
-   *   The following defaults are provided:
-   *   - label: Random string.
-   *   - ID: Random string.
-   *   - region: 'sidebar_first'.
-   *   - theme: The default theme.
-   *   - visibility: Empty array.
-   *
-   * @return \Drupal\block\Entity\Block
-   *   The block entity.
-   *
-   * @todo
-   *   Add support for creating custom block instances.
-   */
-  protected function placeBlock($plugin_id, array $settings = []) {
-    $config = \Drupal::configFactory();
-    $settings += [
-      'plugin' => $plugin_id,
-      'region' => 'sidebar_first',
-      'id' => strtolower($this->randomMachineName(8)),
-      'theme' => $config->get('system.theme')->get('default'),
-      'label' => $this->randomMachineName(8),
-      'visibility' => [],
-      'weight' => 0,
-    ];
-    $values = [];
-    foreach (['region', 'id', 'theme', 'plugin', 'weight', 'visibility'] as $key) {
-      $values[$key] = $settings[$key];
-      // Remove extra values that do not belong in the settings array.
-      unset($settings[$key]);
-    }
-    foreach ($values['visibility'] as $id => $visibility) {
-      $values['visibility'][$id]['id'] = $id;
-    }
-    $values['settings'] = $settings;
-    $block = Block::create($values);
-    $block->save();
-    return $block;
-  }
+  use BaseBlockCreationTrait;
 
 }
diff --git a/core/modules/simpletest/src/ContentTypeCreationTrait.php b/core/modules/simpletest/src/ContentTypeCreationTrait.php
index ec15b9af77..b929893f0a 100644
--- a/core/modules/simpletest/src/ContentTypeCreationTrait.php
+++ b/core/modules/simpletest/src/ContentTypeCreationTrait.php
@@ -2,53 +2,20 @@
 
 namespace Drupal\simpletest;
 
-use Drupal\Component\Render\FormattableMarkup;
-use Drupal\node\Entity\NodeType;
-use PHPUnit\Framework\TestCase;
+use Drupal\Tests\node\Traits\ContentTypeCreationTrait as BaseContentTypeCreationTrait;
 
 /**
  * Provides methods to create content type from given values.
  *
  * This trait is meant to be used only by test classes.
+ *
+ * @deprecated in Drupal 8.4.x. Will be removed before Drupal 9.0.0. Use
+ *   Drupal\Tests\ContentTypeCreationTrait instead.
+ *
+ * @see https://www.drupal.org/node/2884454
  */
 trait ContentTypeCreationTrait {
 
-  /**
-   * Creates a custom content type based on default settings.
-   *
-   * @param array $values
-   *   An array of settings to change from the defaults.
-   *   Example: 'type' => 'foo'.
-   *
-   * @return \Drupal\node\Entity\NodeType
-   *   Created content type.
-   */
-  protected function createContentType(array $values = []) {
-    // Find a non-existent random type name.
-    if (!isset($values['type'])) {
-      do {
-        $id = strtolower($this->randomMachineName(8));
-      } while (NodeType::load($id));
-    }
-    else {
-      $id = $values['type'];
-    }
-    $values += [
-      'type' => $id,
-      'name' => $id,
-    ];
-    $type = NodeType::create($values);
-    $status = $type->save();
-    node_add_body_field($type);
-
-    if ($this instanceof TestCase) {
-      $this->assertSame($status, SAVED_NEW, (new FormattableMarkup('Created content type %type.', ['%type' => $type->id()]))->__toString());
-    }
-    else {
-      $this->assertEqual($status, SAVED_NEW, (new FormattableMarkup('Created content type %type.', ['%type' => $type->id()]))->__toString());
-    }
-
-    return $type;
-  }
+  use BaseContentTypeCreationTrait;
 
 }
diff --git a/core/modules/simpletest/src/NodeCreationTrait.php b/core/modules/simpletest/src/NodeCreationTrait.php
index 20dc3f8379..19351a2e2a 100644
--- a/core/modules/simpletest/src/NodeCreationTrait.php
+++ b/core/modules/simpletest/src/NodeCreationTrait.php
@@ -2,83 +2,20 @@
 
 namespace Drupal\simpletest;
 
-use Drupal\node\Entity\Node;
+use Drupal\Tests\node\Traits\NodeCreationTrait as BaseNodeCreationTrait;
 
 /**
  * Provides methods to create node based on default settings.
  *
  * This trait is meant to be used only by test classes.
+ *
+ * @deprecated in Drupal 8.4.x. Will be removed before Drupal 9.0.0. Use
+ *   Drupal\Tests\NodeCreationTrait instead.
+ *
+ * @see https://www.drupal.org/node/2884454
  */
 trait NodeCreationTrait {
 
-  /**
-   * Get a node from the database based on its title.
-   *
-   * @param string|\Drupal\Component\Render\MarkupInterface $title
-   *   A node title, usually generated by $this->randomMachineName().
-   * @param $reset
-   *   (optional) Whether to reset the entity cache.
-   *
-   * @return \Drupal\node\NodeInterface
-   *   A node entity matching $title.
-   */
-  public function getNodeByTitle($title, $reset = FALSE) {
-    if ($reset) {
-      \Drupal::entityTypeManager()->getStorage('node')->resetCache();
-    }
-    // Cast MarkupInterface objects to string.
-    $title = (string) $title;
-    $nodes = \Drupal::entityTypeManager()
-      ->getStorage('node')
-      ->loadByProperties(['title' => $title]);
-    // Load the first node returned from the database.
-    $returned_node = reset($nodes);
-    return $returned_node;
-  }
-
-  /**
-   * Creates a node based on default settings.
-   *
-   * @param array $settings
-   *   (optional) An associative array of settings for the node, as used in
-   *   entity_create(). Override the defaults by specifying the key and value
-   *   in the array, for example:
-   *   @code
-   *     $this->drupalCreateNode(array(
-   *       'title' => t('Hello, world!'),
-   *       'type' => 'article',
-   *     ));
-   *   @endcode
-   *   The following defaults are provided:
-   *   - body: Random string using the default filter format:
-   *     @code
-   *       $settings['body'][0] = array(
-   *         'value' => $this->randomMachineName(32),
-   *         'format' => filter_default_format(),
-   *       );
-   *     @endcode
-   *   - title: Random string.
-   *   - type: 'page'.
-   *   - uid: The currently logged in user, or anonymous.
-   *
-   * @return \Drupal\node\NodeInterface
-   *   The created node entity.
-   */
-  protected function createNode(array $settings = []) {
-    // Populate defaults array.
-    $settings += [
-      'body'      => [[
-        'value' => $this->randomMachineName(32),
-        'format' => filter_default_format(),
-      ]],
-      'title'     => $this->randomMachineName(8),
-      'type'      => 'page',
-      'uid'       => \Drupal::currentUser()->id(),
-    ];
-    $node = Node::create($settings);
-    $node->save();
-
-    return $node;
-  }
+  use BaseNodeCreationTrait;
 
 }
diff --git a/core/modules/simpletest/src/TestBase.php b/core/modules/simpletest/src/TestBase.php
index 8b33f4be06..a3fd1788d6 100644
--- a/core/modules/simpletest/src/TestBase.php
+++ b/core/modules/simpletest/src/TestBase.php
@@ -12,6 +12,7 @@
 use Drupal\Core\Test\TestDatabase;
 use Drupal\Core\Test\TestSetupTrait;
 use Drupal\Core\Utility\Error;
+use Drupal\Tests\AssertHelperTrait as BaseAssertHelperTrait;
 use Drupal\Tests\ConfigTestTrait;
 use Drupal\Tests\RandomGeneratorTrait;
 use Drupal\Tests\SessionTestTrait;
@@ -24,10 +25,10 @@
  */
 abstract class TestBase {
 
+  use BaseAssertHelperTrait;
   use TestSetupTrait;
   use SessionTestTrait;
   use RandomGeneratorTrait;
-  use AssertHelperTrait;
   use GeneratePermutationsTrait;
   // For backwards compatibility switch the visbility of the methods to public.
   use ConfigTestTrait {
diff --git a/core/modules/simpletest/src/UserCreationTrait.php b/core/modules/simpletest/src/UserCreationTrait.php
index 4b4d0ec956..f97ec5ccc2 100644
--- a/core/modules/simpletest/src/UserCreationTrait.php
+++ b/core/modules/simpletest/src/UserCreationTrait.php
@@ -2,11 +2,7 @@
 
 namespace Drupal\simpletest;
 
-use Drupal\Component\Utility\SafeMarkup;
-use Drupal\Core\Session\AccountInterface;
-use Drupal\user\Entity\Role;
-use Drupal\user\Entity\User;
-use Drupal\user\RoleInterface;
+use Drupal\Tests\user\Traits\UserCreationTrait as BaseUserCreationTrait;
 
 /**
  * Provides methods to create additional test users and switch the currently
@@ -14,201 +10,14 @@
  *
  * This trait is meant to be used only by test classes extending
  * \Drupal\simpletest\TestBase.
+ *
+ * @deprecated in Drupal 8.4.x. Will be removed before Drupal 9.0.0. Use
+ *   Drupal\Tests\UserCreationTrait instead.
+ *
+ * @see https://www.drupal.org/node/2884454
  */
 trait UserCreationTrait {
 
-  /**
-   * Switch the current logged in user.
-   *
-   * @param \Drupal\Core\Session\AccountInterface $account
-   *   The user account object.
-   */
-  protected function setCurrentUser(AccountInterface $account) {
-    \Drupal::currentUser()->setAccount($account);
-  }
-
-  /**
-   * Create a user with a given set of permissions.
-   *
-   * @param array $permissions
-   *   Array of permission names to assign to user. Note that the user always
-   *   has the default permissions derived from the "authenticated users" role.
-   * @param string $name
-   *   The user name.
-   * @param bool $admin
-   *   (optional) Whether the user should be an administrator
-   *   with all the available permissions.
-   *
-   * @return \Drupal\user\Entity\User|false
-   *   A fully loaded user object with pass_raw property, or FALSE if account
-   *   creation fails.
-   */
-  protected function createUser(array $permissions = [], $name = NULL, $admin = FALSE) {
-    // Create a role with the given permission set, if any.
-    $rid = FALSE;
-    if ($permissions) {
-      $rid = $this->createRole($permissions);
-      if (!$rid) {
-        return FALSE;
-      }
-    }
-
-    // Create a user assigned to that role.
-    $edit = [];
-    $edit['name'] = !empty($name) ? $name : $this->randomMachineName();
-    $edit['mail'] = $edit['name'] . '@example.com';
-    $edit['pass'] = user_password();
-    $edit['status'] = 1;
-    if ($rid) {
-      $edit['roles'] = [$rid];
-    }
-
-    if ($admin) {
-      $edit['roles'][] = $this->createAdminRole();
-    }
-
-    $account = User::create($edit);
-    $account->save();
-
-    $this->assertTrue($account->id(), SafeMarkup::format('User created with name %name and pass %pass', ['%name' => $edit['name'], '%pass' => $edit['pass']]), 'User login');
-    if (!$account->id()) {
-      return FALSE;
-    }
-
-    // Add the raw password so that we can log in as this user.
-    $account->pass_raw = $edit['pass'];
-    // Support BrowserTestBase as well.
-    $account->passRaw = $account->pass_raw;
-    return $account;
-  }
-
-  /**
-   * Creates an administrative role.
-   *
-   * @param string $rid
-   *   (optional) The role ID (machine name). Defaults to a random name.
-   * @param string $name
-   *   (optional) The label for the role. Defaults to a random string.
-   * @param int $weight
-   *   (optional) The weight for the role. Defaults NULL so that entity_create()
-   *   sets the weight to maximum + 1.
-   *
-   * @return string
-   *   Role ID of newly created role, or FALSE if role creation failed.
-   */
-  protected function createAdminRole($rid = NULL, $name = NULL, $weight = NULL) {
-    $rid = $this->createRole([], $rid, $name, $weight);
-    if ($rid) {
-      /** @var \Drupal\user\RoleInterface $role */
-      $role = Role::load($rid);
-      $role->setIsAdmin(TRUE);
-      $role->save();
-    }
-    return $rid;
-  }
-
-  /**
-   * Creates a role with specified permissions.
-   *
-   * @param array $permissions
-   *   Array of permission names to assign to role.
-   * @param string $rid
-   *   (optional) The role ID (machine name). Defaults to a random name.
-   * @param string $name
-   *   (optional) The label for the role. Defaults to a random string.
-   * @param int $weight
-   *   (optional) The weight for the role. Defaults NULL so that entity_create()
-   *   sets the weight to maximum + 1.
-   *
-   * @return string
-   *   Role ID of newly created role, or FALSE if role creation failed.
-   */
-  protected function createRole(array $permissions, $rid = NULL, $name = NULL, $weight = NULL) {
-    // Generate a random, lowercase machine name if none was passed.
-    if (!isset($rid)) {
-      $rid = strtolower($this->randomMachineName(8));
-    }
-    // Generate a random label.
-    if (!isset($name)) {
-      // In the role UI role names are trimmed and random string can start or
-      // end with a space.
-      $name = trim($this->randomString(8));
-    }
-
-    // Check the all the permissions strings are valid.
-    if (!$this->checkPermissions($permissions)) {
-      return FALSE;
-    }
-
-    // Create new role.
-    $role = Role::create([
-      'id' => $rid,
-      'label' => $name,
-    ]);
-    if (isset($weight)) {
-      $role->set('weight', $weight);
-    }
-    $result = $role->save();
-
-    $this->assertIdentical($result, SAVED_NEW, SafeMarkup::format('Created role ID @rid with name @name.', [
-      '@name' => var_export($role->label(), TRUE),
-      '@rid' => var_export($role->id(), TRUE),
-    ]), 'Role');
-
-    if ($result === SAVED_NEW) {
-      // Grant the specified permissions to the role, if any.
-      if (!empty($permissions)) {
-        $this->grantPermissions($role, $permissions);
-        $assigned_permissions = Role::load($role->id())->getPermissions();
-        $missing_permissions = array_diff($permissions, $assigned_permissions);
-        if (!$missing_permissions) {
-          $this->pass(SafeMarkup::format('Created permissions: @perms', ['@perms' => implode(', ', $permissions)]), 'Role');
-        }
-        else {
-          $this->fail(SafeMarkup::format('Failed to create permissions: @perms', ['@perms' => implode(', ', $missing_permissions)]), 'Role');
-        }
-      }
-      return $role->id();
-    }
-    else {
-      return FALSE;
-    }
-  }
-
-  /**
-   * Checks whether a given list of permission names is valid.
-   *
-   * @param array $permissions
-   *   The permission names to check.
-   *
-   * @return bool
-   *   TRUE if the permissions are valid, FALSE otherwise.
-   */
-  protected function checkPermissions(array $permissions) {
-    $available = array_keys(\Drupal::service('user.permissions')->getPermissions());
-    $valid = TRUE;
-    foreach ($permissions as $permission) {
-      if (!in_array($permission, $available)) {
-        $this->fail(SafeMarkup::format('Invalid permission %permission.', ['%permission' => $permission]), 'Role');
-        $valid = FALSE;
-      }
-    }
-    return $valid;
-  }
-
-  /**
-   * Grant permissions to a user role.
-   *
-   * @param \Drupal\user\RoleInterface $role
-   *   The ID of a user role to alter.
-   * @param array $permissions
-   *   (optional) A list of permission names to grant.
-   */
-  protected function grantPermissions(RoleInterface $role, array $permissions) {
-    foreach ($permissions as $permission) {
-      $role->grantPermission($permission);
-    }
-    $role->trustData()->save();
-  }
+  use BaseUserCreationTrait;
 
 }
diff --git a/core/modules/simpletest/src/WebTestBase.php b/core/modules/simpletest/src/WebTestBase.php
index 975d95bd9a..1e02255395 100644
--- a/core/modules/simpletest/src/WebTestBase.php
+++ b/core/modules/simpletest/src/WebTestBase.php
@@ -18,8 +18,12 @@
 use Drupal\Core\Url;
 use Drupal\system\Tests\Cache\AssertPageCacheContextsAndTagsTrait;
 use Drupal\Tests\EntityViewTrait;
+use Drupal\Tests\block\Traits\BlockCreationTrait as BaseBlockCreationTrait;
+use Drupal\Tests\node\Traits\ContentTypeCreationTrait;
+use Drupal\Tests\node\Traits\NodeCreationTrait;
 use Drupal\Tests\Traits\Core\CronRunTrait;
 use Drupal\Tests\TestFileCreationTrait;
+use Drupal\Tests\user\Traits\UserCreationTrait;
 use Drupal\Tests\XdebugRequestTrait;
 use Zend\Diactoros\Uri;
 
@@ -37,7 +41,7 @@
     compareFiles as drupalCompareFiles;
   }
   use AssertPageCacheContextsAndTagsTrait;
-  use BlockCreationTrait {
+  use BaseBlockCreationTrait {
     placeBlock as drupalPlaceBlock;
   }
   use ContentTypeCreationTrait {
diff --git a/core/modules/simpletest/src/UserCreationTrait.php b/core/modules/user/tests/src/Traits/UserCreationTrait.php
similarity index 98%
copy from core/modules/simpletest/src/UserCreationTrait.php
copy to core/modules/user/tests/src/Traits/UserCreationTrait.php
index 4b4d0ec956..ccccfa77ff 100644
--- a/core/modules/simpletest/src/UserCreationTrait.php
+++ b/core/modules/user/tests/src/Traits/UserCreationTrait.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace Drupal\simpletest;
+namespace Drupal\Tests\user\Traits;
 
 use Drupal\Component\Utility\SafeMarkup;
 use Drupal\Core\Session\AccountInterface;
@@ -12,8 +12,7 @@
  * Provides methods to create additional test users and switch the currently
  * logged in one.
  *
- * This trait is meant to be used only by test classes extending
- * \Drupal\simpletest\TestBase.
+ * This trait is meant to be used only by test classes.
  */
 trait UserCreationTrait {
 
diff --git a/core/tests/Drupal/KernelTests/KernelTestBase.php b/core/tests/Drupal/KernelTests/KernelTestBase.php
index 6a35f15373..09a82c3483 100644
--- a/core/tests/Drupal/KernelTests/KernelTestBase.php
+++ b/core/tests/Drupal/KernelTests/KernelTestBase.php
@@ -18,7 +18,7 @@
 use Drupal\Core\Site\Settings;
 use Drupal\Core\Test\TestDatabase;
 use Drupal\simpletest\AssertContentTrait;
-use Drupal\simpletest\AssertHelperTrait;
+use Drupal\Tests\AssertHelperTrait;
 use Drupal\Tests\ConfigTestTrait;
 use Drupal\Tests\RandomGeneratorTrait;
 use Drupal\simpletest\TestServiceProvider;
diff --git a/core/modules/simpletest/src/AssertHelperTrait.php b/core/tests/Drupal/Tests/AssertHelperTrait.php
similarity index 96%
copy from core/modules/simpletest/src/AssertHelperTrait.php
copy to core/tests/Drupal/Tests/AssertHelperTrait.php
index 5325e8c9b0..ba814d9641 100644
--- a/core/modules/simpletest/src/AssertHelperTrait.php
+++ b/core/tests/Drupal/Tests/AssertHelperTrait.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace Drupal\simpletest;
+namespace Drupal\Tests;
 
 use Drupal\Component\Render\MarkupInterface;
 
diff --git a/core/modules/simpletest/tests/src/Unit/AssertHelperTraitTest.php b/core/tests/Drupal/Tests/AssertHelperTraitTest.php
similarity index 80%
rename from core/modules/simpletest/tests/src/Unit/AssertHelperTraitTest.php
rename to core/tests/Drupal/Tests/AssertHelperTraitTest.php
index 8c816b0bbe..f2e7eca6c7 100644
--- a/core/modules/simpletest/tests/src/Unit/AssertHelperTraitTest.php
+++ b/core/tests/Drupal/Tests/AssertHelperTraitTest.php
@@ -1,19 +1,13 @@
 <?php
 
-/**
- * @file
- * Contains \Drupal\Tests\simpletest\Unit\AssertHelperTraitTest.
- */
-
-namespace Drupal\Tests\simpletest\Unit;
+namespace Drupal\Tests;
 
 use Drupal\Core\Render\Markup;
-use Drupal\simpletest\AssertHelperTrait;
-use Drupal\Tests\UnitTestCase;
 
 /**
- * @coversDefaultClass \Drupal\simpletest\AssertHelperTrait
+ * @coversDefaultClass \Drupal\Tests\AssertHelperTrait
  * @group simpletest
+ * @group Tests
  */
 class AssertHelperTraitTest extends UnitTestCase {
 
diff --git a/core/tests/Drupal/Tests/BrowserTestBase.php b/core/tests/Drupal/Tests/BrowserTestBase.php
index bd50c23b48..e2ed3876a1 100644
--- a/core/tests/Drupal/Tests/BrowserTestBase.php
+++ b/core/tests/Drupal/Tests/BrowserTestBase.php
@@ -22,11 +22,10 @@
 use Drupal\Core\Url;
 use Drupal\Core\Utility\Error;
 use Drupal\FunctionalTests\AssertLegacyTrait;
-use Drupal\simpletest\AssertHelperTrait;
-use Drupal\simpletest\BlockCreationTrait;
-use Drupal\simpletest\ContentTypeCreationTrait;
-use Drupal\simpletest\NodeCreationTrait;
-use Drupal\simpletest\UserCreationTrait;
+use Drupal\Tests\block\Traits\BlockCreationTrait;
+use Drupal\Tests\node\Traits\ContentTypeCreationTrait;
+use Drupal\Tests\node\Traits\NodeCreationTrait;
+use Drupal\Tests\user\Traits\UserCreationTrait;
 use PHPUnit\Framework\TestCase;
 use Psr\Http\Message\RequestInterface;
 use Psr\Http\Message\ResponseInterface;
