core/modules/rest/config/install/rest.settings.yml |   7 -
 core/modules/rest/config/schema/rest.schema.yml    |  14 -
 core/modules/rest/rest.api.php                     |  57 --
 core/modules/rest/rest.install                     |  60 --
 core/modules/rest/rest.post_update.php             |  63 ---
 core/modules/rest/rest.routing.yml                 |   9 -
 core/modules/rest/rest.services.yml                |  15 -
 .../src/EventSubscriber/RestConfigSubscriber.php   |  53 --
 .../ConfigurableLinkManagerInterface.php           |  13 -
 core/modules/rest/src/LinkManager/LinkManager.php  |  13 -
 .../rest/src/LinkManager/LinkManagerBase.php       |  13 -
 .../rest/src/LinkManager/LinkManagerInterface.php  |  13 -
 .../rest/src/LinkManager/RelationLinkManager.php   |  13 -
 .../LinkManager/RelationLinkManagerInterface.php   |  13 -
 .../rest/src/LinkManager/TypeLinkManager.php       |  13 -
 .../src/LinkManager/TypeLinkManagerInterface.php   |  13 -
 .../PathProcessorEntityResourceBC.php              |  55 --
 core/modules/rest/src/Plugin/ResourceBase.php      |   8 -
 .../src/Plugin/rest/resource/EntityResource.php    |  10 +-
 core/modules/rest/src/RestServiceProvider.php      |  51 --
 core/modules/rest/src/Tests/RESTTestBase.php       | 624 ---------------------
 ....rest-rest_post_update_resource_granularity.php | Bin 5199 -> 0 bytes
 .../update/drupal-8.rest-rest_update_8201.php      |  59 --
 .../update/drupal-8.rest-rest_update_8203.php      |  58 --
 .../update/rest-export-with-authentication.php     |  65 ---
 .../rest.resource.entity.comment_2721595.yml       |  32 --
 .../update/rest.resource.entity.node_2721595.yml   |  29 -
 .../update/rest.resource.entity.user_2721595.yml   |  32 --
 .../BcTimestampNormalizerUnixTestTrait.php         |  43 --
 .../BaseFieldOverrideResourceTestBase.php          |   4 -
 .../EntityResource/Block/BlockResourceTestBase.php |   4 -
 .../Comment/CommentResourceTestBase.php            |  17 +-
 .../Editor/EditorResourceTestBase.php              |   4 -
 .../EntityResource/EntityResourceTestBase.php      | 171 ------
 .../EntityTest/EntityTestResourceTestBase.php      |  12 +-
 .../EntityTestLabelResourceTestBase.php            |  12 +-
 .../EntityResource/Feed/FeedResourceTestBase.php   |  22 +-
 .../FieldConfig/FieldConfigResourceTestBase.php    |   4 -
 .../FieldStorageConfigResourceTestBase.php         |   4 -
 .../ImageStyle/ImageStyleResourceTestBase.php      |   4 -
 .../EntityResource/Item/ItemResourceTestBase.php   |  12 +-
 .../MenuLinkContentResourceTestBase.php            |  12 +-
 .../EntityResource/Node/NodeResourceTestBase.php   |  22 +-
 .../NodeType/NodeTypeResourceTestBase.php          |   4 -
 .../SearchPage/SearchPageResourceTestBase.php      |   4 -
 .../Shortcut/ShortcutResourceTestBase.php          |   4 -
 .../EntityResource/Term/TermResourceTestBase.php   |  12 +-
 .../EntityResource/Tour/TourResourceTestBase.php   |   4 -
 .../EntityResource/User/UserResourceTestBase.php   |  17 +-
 .../Update/EntityResourcePermissionsUpdateTest.php |  56 --
 .../Update/ResourceGranularityUpdateTest.php       |  71 ---
 .../Update/RestConfigurationEntitiesUpdateTest.php |  65 ---
 .../Functional/Update/RestExportAuthUpdateTest.php |  36 --
 53 files changed, 62 insertions(+), 1963 deletions(-)

diff --git a/core/modules/rest/config/install/rest.settings.yml b/core/modules/rest/config/install/rest.settings.yml
deleted file mode 100644
index 8f70c69..0000000
--- a/core/modules/rest/config/install/rest.settings.yml
+++ /dev/null
@@ -1,7 +0,0 @@
-# Before Drupal 8.2, EntityResource used permissions as well as the entity
-# access system for access checking. This was confusing, and it only did this
-# for historical reasons. New Drupal installations opt out from this by default
-# (hence this is set to false), existing installations opt in to it.
-# @see rest_update_8203()
-# @see https://www.drupal.org/node/2664780
-bc_entity_resource_permissions: false
diff --git a/core/modules/rest/config/schema/rest.schema.yml b/core/modules/rest/config/schema/rest.schema.yml
index 98b35ae..467ae5b 100644
--- a/core/modules/rest/config/schema/rest.schema.yml
+++ b/core/modules/rest/config/schema/rest.schema.yml
@@ -1,17 +1,3 @@
-# Schema for the configuration files of the REST module.
-rest.settings:
-  type: config_object
-  label: 'REST settings'
-  mapping:
-    # @deprecated in Drupal 8.3.x and will be removed before Drupal 9.0.0.
-    # @see https://www.drupal.org/node/2830467
-    link_domain:
-      type: string
-      label: 'Domain of the relation'
-    bc_entity_resource_permissions:
-      type: boolean
-      label: 'Whether the pre Drupal 8.2.x behavior of having permissions for EntityResource is enabled or not.'
-
 # Method-level granularity of REST resource configuration.
 rest_resource.method:
   type: mapping
diff --git a/core/modules/rest/rest.api.php b/core/modules/rest/rest.api.php
index 6c09bbf..2f3f6ee 100644
--- a/core/modules/rest/rest.api.php
+++ b/core/modules/rest/rest.api.php
@@ -29,62 +29,5 @@ function hook_rest_resource_alter(&$definitions) {
 }
 
 /**
- * Alter the REST type URI.
- *
- * @deprecated in Drupal 8.3.x and will be removed before Drupal 9.0.0. Use
- *   hook_serialization_type_uri_alter() instead. This exists solely for BC.
- *
- * @see https://www.drupal.org/node/2830467
- *
- * Modules may wish to alter the type URI generated for a resource based on the
- * context of the serializer/normalizer operation.
- *
- * @param string $uri
- *   The URI to alter.
- * @param array $context
- *   The context from the serializer/normalizer operation.
- *
- * @see \Symfony\Component\Serializer\SerializerInterface::serialize()
- * @see \Symfony\Component\Serializer\SerializerInterface::deserialize()
- * @see \Symfony\Component\Serializer\NormalizerInterface::normalize()
- * @see \Symfony\Component\Serializer\DenormalizerInterface::denormalize()
- */
-function hook_rest_type_uri_alter(&$uri, $context = []) {
-  if ($context['mymodule'] == TRUE) {
-    $base = \Drupal::config('serialization.settings')->get('link_domain');
-    $uri = str_replace($base, 'http://mymodule.domain', $uri);
-  }
-}
-
-
-/**
- * Alter the REST relation URI.
- *
- * @deprecated in Drupal 8.3.x and will be removed before Drupal 9.0.0. Use
- *   hook_serialization_relation_uri_alter() instead. This exists solely for BC.
- *
- * @see https://www.drupal.org/node/2830467
- *
- * Modules may wish to alter the relation URI generated for a resource based on
- * the context of the serializer/normalizer operation.
- *
- * @param string $uri
- *   The URI to alter.
- * @param array $context
- *   The context from the serializer/normalizer operation.
- *
- * @see \Symfony\Component\Serializer\SerializerInterface::serialize()
- * @see \Symfony\Component\Serializer\SerializerInterface::deserialize()
- * @see \Symfony\Component\Serializer\NormalizerInterface::normalize()
- * @see \Symfony\Component\Serializer\DenormalizerInterface::denormalize()
- */
-function hook_rest_relation_uri_alter(&$uri, $context = []) {
-  if ($context['mymodule'] == TRUE) {
-    $base = \Drupal::config('serialization.settings')->get('link_domain');
-    $uri = str_replace($base, 'http://mymodule.domain', $uri);
-  }
-}
-
-/**
  * @} End of "addtogroup hooks".
  */
diff --git a/core/modules/rest/rest.install b/core/modules/rest/rest.install
index 32c5b1d..c2d9412 100644
--- a/core/modules/rest/rest.install
+++ b/core/modules/rest/rest.install
@@ -24,63 +24,3 @@ function rest_requirements($phase) {
   }
   return $requirements;
 }
-
-/**
- * Install the REST config entity type and fix old settings-based config.
- *
- * @see rest_post_update_create_rest_resource_config_entities()
- */
-function rest_update_8201() {
-  \Drupal::entityDefinitionUpdateManager()->installEntityType(new ConfigEntityType([
-    'id' => 'rest_resource_config',
-    'label' => new TranslatableMarkup('REST resource configuration'),
-    'config_prefix' => 'resource',
-    'admin_permission' => 'administer rest resources',
-    'label_callback' => 'getLabelFromPlugin',
-    'entity_keys' => ['id' => 'id'],
-    'config_export' => [
-      'id',
-      'plugin_id',
-      'granularity',
-      'configuration',
-    ],
-  ]));
-  \Drupal::state()->set('rest_update_8201_resources', \Drupal::config('rest.settings')->get('resources'));
-  \Drupal::configFactory()->getEditable('rest.settings')
-    ->clear('resources')
-    ->save();
-}
-
-/**
- * Re-save all views with a REST display to add new auth defaults.
- */
-function rest_update_8202() {
-  $config_factory = \Drupal::configFactory();
-  foreach ($config_factory->listAll('views.view.') as $view_config_name) {
-    $save = FALSE;
-    $view = $config_factory->getEditable($view_config_name);
-    $displays = $view->get('display');
-    foreach ($displays as $display_name => &$display) {
-      if ($display['display_plugin'] == 'rest_export') {
-        if (!isset($display['display_options']['auth'])) {
-          $display['display_options']['auth'] = [];
-          $save = TRUE;
-        }
-      }
-    }
-    if ($save) {
-      $view->set('display', $displays);
-      $view->save(TRUE);
-    }
-  }
-}
-
-/**
- * Enable BC for EntityResource: continue to use permissions.
- */
-function rest_update_8203() {
-  $config_factory = \Drupal::configFactory();
-  $rest_settings = $config_factory->getEditable('rest.settings');
-  $rest_settings->set('bc_entity_resource_permissions', TRUE)
-    ->save(TRUE);
-}
diff --git a/core/modules/rest/rest.post_update.php b/core/modules/rest/rest.post_update.php
deleted file mode 100644
index 6d45178..0000000
--- a/core/modules/rest/rest.post_update.php
+++ /dev/null
@@ -1,63 +0,0 @@
-<?php
-
-/**
- * @file
- * Post update functions for Rest.
- */
-
-use Drupal\rest\Entity\RestResourceConfig;
-use Drupal\rest\RestResourceConfigInterface;
-
-/**
- * Create REST resource configuration entities.
- *
- * @see rest_update_8201()
- * @see https://www.drupal.org/node/2308745
- */
-function rest_post_update_create_rest_resource_config_entities() {
-  $resources = \Drupal::state()->get('rest_update_8201_resources', []);
-  foreach ($resources as $key => $resource) {
-    $resource = RestResourceConfig::create([
-      'id' => str_replace(':', '.', $key),
-      'granularity' => RestResourceConfigInterface::METHOD_GRANULARITY,
-      'configuration' => $resource,
-    ]);
-    $resource->save();
-  }
-}
-
-/**
- * Simplify method-granularity REST resource config to resource-granularity.
- *
- * @see https://www.drupal.org/node/2721595
- */
-function rest_post_update_resource_granularity() {
-  /** @var \Drupal\rest\RestResourceConfigInterface[] $resource_config_entities */
-  $resource_config_entities = RestResourceConfig::loadMultiple();
-
-  foreach ($resource_config_entities as $resource_config_entity) {
-    if ($resource_config_entity->get('granularity') === RestResourceConfigInterface::METHOD_GRANULARITY) {
-      $configuration = $resource_config_entity->get('configuration');
-
-      $format_and_auth_configuration = [];
-      foreach (array_keys($configuration) as $method) {
-        $format_and_auth_configuration['format'][$method] = implode(',', $configuration[$method]['supported_formats']);
-        $format_and_auth_configuration['auth'][$method] = implode(',', $configuration[$method]['supported_auth']);
-      }
-
-      // If each method has the same formats and the same authentication
-      // providers configured, convert it to 'granularity: resource', which has
-      // a simpler/less verbose configuration.
-      if (count(array_unique($format_and_auth_configuration['format'])) === 1 && count(array_unique($format_and_auth_configuration['auth'])) === 1) {
-        $first_method = array_keys($configuration)[0];
-        $resource_config_entity->set('configuration', [
-          'methods' => array_keys($configuration),
-          'formats' => $configuration[$first_method]['supported_formats'],
-          'authentication' => $configuration[$first_method]['supported_auth']
-        ]);
-        $resource_config_entity->set('granularity', RestResourceConfigInterface::RESOURCE_GRANULARITY);
-        $resource_config_entity->save();
-      }
-    }
-  }
-}
diff --git a/core/modules/rest/rest.routing.yml b/core/modules/rest/rest.routing.yml
deleted file mode 100644
index ba7dd03..0000000
--- a/core/modules/rest/rest.routing.yml
+++ /dev/null
@@ -1,9 +0,0 @@
-# @deprecated This route is deprecated, use the system.csrftoken route from the
-# system module instead.
-# @todo Remove this route in Drupal 9.0.0.
-rest.csrftoken:
-  path: '/rest/session/token'
-  defaults:
-    _controller: '\Drupal\system\Controller\CsrfTokenController::csrfToken'
-  requirements:
-    _access: 'TRUE'
diff --git a/core/modules/rest/rest.services.yml b/core/modules/rest/rest.services.yml
index 080a681..5ffb8de 100644
--- a/core/modules/rest/rest.services.yml
+++ b/core/modules/rest/rest.services.yml
@@ -8,9 +8,6 @@ services:
       - { name: cache.bin }
     factory: cache_factory:get
     arguments: [rest]
-  # @todo Remove this service in Drupal 9.0.0.
-  access_check.rest.csrf:
-    alias: access_check.header.csrf
   rest.resource_routes:
     class: Drupal\rest\Routing\ResourceRoutes
     arguments: ['@plugin.manager.rest', '@entity_type.manager', '@logger.channel.rest']
@@ -26,20 +23,8 @@ services:
     tags:
       - { name: event_subscriber }
     arguments: ['@serializer', '@renderer', '@current_route_match']
-  rest.config_subscriber:
-    class: Drupal\rest\EventSubscriber\RestConfigSubscriber
-    arguments: ['@router.builder']
-    tags:
-      - { name: event_subscriber }
   rest.resource.entity.post_route.subscriber:
     class: \Drupal\rest\EventSubscriber\EntityResourcePostRouteSubscriber
     arguments: ['@entity_type.manager']
     tags:
       - { name: event_subscriber }
-
-  # @todo Remove in Drupal 9.0.0.
-  rest.path_processor_entity_resource_bc:
-    class: \Drupal\rest\PathProcessor\PathProcessorEntityResourceBC
-    arguments: ['@entity_type.manager']
-    tags:
-      - { name: path_processor_inbound }
diff --git a/core/modules/rest/src/EventSubscriber/RestConfigSubscriber.php b/core/modules/rest/src/EventSubscriber/RestConfigSubscriber.php
deleted file mode 100644
index d199545..0000000
--- a/core/modules/rest/src/EventSubscriber/RestConfigSubscriber.php
+++ /dev/null
@@ -1,53 +0,0 @@
-<?php
-
-namespace Drupal\rest\EventSubscriber;
-
-use Drupal\Core\Config\ConfigCrudEvent;
-use Drupal\Core\Config\ConfigEvents;
-use Drupal\Core\Routing\RouteBuilderInterface;
-use Symfony\Component\EventDispatcher\EventSubscriberInterface;
-
-/**
- * A subscriber triggering a route rebuild when certain configuration changes.
- */
-class RestConfigSubscriber implements EventSubscriberInterface {
-
-  /**
-   * The router builder.
-   *
-   * @var \Drupal\Core\Routing\RouteBuilderInterface
-   */
-  protected $routerBuilder;
-
-  /**
-   * Constructs the RestConfigSubscriber.
-   *
-   * @param \Drupal\Core\Routing\RouteBuilderInterface $router_builder
-   *   The router builder service.
-   */
-  public function __construct(RouteBuilderInterface $router_builder) {
-    $this->routerBuilder = $router_builder;
-  }
-
-  /**
-   * Informs the router builder a rebuild is needed when necessary.
-   *
-   * @param \Drupal\Core\Config\ConfigCrudEvent $event
-   *   The Event to process.
-   */
-  public function onSave(ConfigCrudEvent $event) {
-    $saved_config = $event->getConfig();
-    if ($saved_config->getName() === 'rest.settings' && $event->isChanged('bc_entity_resource_permissions')) {
-      $this->routerBuilder->setRebuildNeeded();
-    }
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public static function getSubscribedEvents() {
-    $events[ConfigEvents::SAVE][] = ['onSave'];
-    return $events;
-  }
-
-}
diff --git a/core/modules/rest/src/LinkManager/ConfigurableLinkManagerInterface.php b/core/modules/rest/src/LinkManager/ConfigurableLinkManagerInterface.php
deleted file mode 100644
index e521459..0000000
--- a/core/modules/rest/src/LinkManager/ConfigurableLinkManagerInterface.php
+++ /dev/null
@@ -1,13 +0,0 @@
-<?php
-
-namespace Drupal\rest\LinkManager;
-
-use Drupal\hal\LinkManager\ConfigurableLinkManagerInterface as MovedConfigurableLinkManagerInterface;
-
-/**
- * @deprecated in Drupal 8.3.x and will be removed before Drupal 9.0.0. This has
- *   been moved to the hal module. This exists solely for BC.
- *
- * @see https://www.drupal.org/node/2830467
- */
-interface ConfigurableLinkManagerInterface extends MovedConfigurableLinkManagerInterface {}
diff --git a/core/modules/rest/src/LinkManager/LinkManager.php b/core/modules/rest/src/LinkManager/LinkManager.php
deleted file mode 100644
index 4586c62..0000000
--- a/core/modules/rest/src/LinkManager/LinkManager.php
+++ /dev/null
@@ -1,13 +0,0 @@
-<?php
-
-namespace Drupal\rest\LinkManager;
-
-use Drupal\hal\LinkManager\LinkManager as MovedLinkManager;
-
-/**
- * @deprecated in Drupal 8.3.x and will be removed before Drupal 9.0.0. This has
- *   been moved to the hal module. This exists solely for BC.
- *
- * @see https://www.drupal.org/node/2830467
- */
-class LinkManager extends MovedLinkManager implements LinkManagerInterface {}
diff --git a/core/modules/rest/src/LinkManager/LinkManagerBase.php b/core/modules/rest/src/LinkManager/LinkManagerBase.php
deleted file mode 100644
index 85eb7b7..0000000
--- a/core/modules/rest/src/LinkManager/LinkManagerBase.php
+++ /dev/null
@@ -1,13 +0,0 @@
-<?php
-
-namespace Drupal\rest\LinkManager;
-
-use Drupal\hal\LinkManager\LinkManagerBase as MovedLinkManagerBase;
-
-/**
- * @deprecated in Drupal 8.3.x and will be removed before Drupal 9.0.0. This has
- *   been moved to the hal module. This exists solely for BC.
- *
- * @see https://www.drupal.org/node/2830467
- */
-abstract class LinkManagerBase extends MovedLinkManagerBase {}
diff --git a/core/modules/rest/src/LinkManager/LinkManagerInterface.php b/core/modules/rest/src/LinkManager/LinkManagerInterface.php
deleted file mode 100644
index 9f5d2f2..0000000
--- a/core/modules/rest/src/LinkManager/LinkManagerInterface.php
+++ /dev/null
@@ -1,13 +0,0 @@
-<?php
-
-namespace Drupal\rest\LinkManager;
-
-use Drupal\hal\LinkManager\LinkManagerInterface as MovedLinkManagerInterface;
-
-/**
- * @deprecated in Drupal 8.3.x and will be removed before Drupal 9.0.0. This has
- *   been moved to the hal module. This exists solely for BC.
- *
- * @see https://www.drupal.org/node/2830467
- */
-interface LinkManagerInterface extends MovedLinkManagerInterface {}
diff --git a/core/modules/rest/src/LinkManager/RelationLinkManager.php b/core/modules/rest/src/LinkManager/RelationLinkManager.php
deleted file mode 100644
index 6690e21..0000000
--- a/core/modules/rest/src/LinkManager/RelationLinkManager.php
+++ /dev/null
@@ -1,13 +0,0 @@
-<?php
-
-namespace Drupal\rest\LinkManager;
-
-use Drupal\hal\LinkManager\RelationLinkManager as MovedLinkRelationManager;
-
-/**
- * @deprecated in Drupal 8.3.x and will be removed before Drupal 9.0.0. This has
- *   been moved to the hal module. This exists solely for BC.
- *
- * @see https://www.drupal.org/node/2830467
- */
-class RelationLinkManager extends MovedLinkRelationManager implements RelationLinkManagerInterface {}
diff --git a/core/modules/rest/src/LinkManager/RelationLinkManagerInterface.php b/core/modules/rest/src/LinkManager/RelationLinkManagerInterface.php
deleted file mode 100644
index c2eec34..0000000
--- a/core/modules/rest/src/LinkManager/RelationLinkManagerInterface.php
+++ /dev/null
@@ -1,13 +0,0 @@
-<?php
-
-namespace Drupal\rest\LinkManager;
-
-use Drupal\hal\LinkManager\RelationLinkManagerInterface as MovedRelationLinkManagerInterface;
-
-/**
- * @deprecated in Drupal 8.3.x and will be removed before Drupal 9.0.0. This has
- *   been moved to the hal module. This exists solely for BC.
- *
- * @see https://www.drupal.org/node/2830467
- */
-interface RelationLinkManagerInterface extends MovedRelationLinkManagerInterface {}
diff --git a/core/modules/rest/src/LinkManager/TypeLinkManager.php b/core/modules/rest/src/LinkManager/TypeLinkManager.php
deleted file mode 100644
index 6d7ba03..0000000
--- a/core/modules/rest/src/LinkManager/TypeLinkManager.php
+++ /dev/null
@@ -1,13 +0,0 @@
-<?php
-
-namespace Drupal\rest\LinkManager;
-
-use Drupal\hal\LinkManager\TypeLinkManager as MovedTypeLinkManager;
-
-/**
- * @deprecated in Drupal 8.3.x and will be removed before Drupal 9.0.0. This has
- *   been moved to the hal module. This exists solely for BC.
- *
- * @see https://www.drupal.org/node/2830467
- */
-class TypeLinkManager extends MovedTypeLinkManager implements TypeLinkManagerInterface {}
diff --git a/core/modules/rest/src/LinkManager/TypeLinkManagerInterface.php b/core/modules/rest/src/LinkManager/TypeLinkManagerInterface.php
deleted file mode 100644
index 9a37049..0000000
--- a/core/modules/rest/src/LinkManager/TypeLinkManagerInterface.php
+++ /dev/null
@@ -1,13 +0,0 @@
-<?php
-
-namespace Drupal\rest\LinkManager;
-
-use Drupal\hal\LinkManager\TypeLinkManagerInterface as MovedTypeLinkManagerInterface;
-
-/**
- * @deprecated in Drupal 8.3.x and will be removed before Drupal 9.0.0. This has
- *   been moved to the hal module. This exists solely for BC.
- *
- * @see https://www.drupal.org/node/2830467
- */
-interface TypeLinkManagerInterface extends MovedTypeLinkManagerInterface {}
diff --git a/core/modules/rest/src/PathProcessor/PathProcessorEntityResourceBC.php b/core/modules/rest/src/PathProcessor/PathProcessorEntityResourceBC.php
deleted file mode 100644
index 1f68691..0000000
--- a/core/modules/rest/src/PathProcessor/PathProcessorEntityResourceBC.php
+++ /dev/null
@@ -1,55 +0,0 @@
-<?php
-
-namespace Drupal\rest\PathProcessor;
-
-use Drupal\Core\Entity\EntityTypeManagerInterface;
-use Drupal\Core\PathProcessor\InboundPathProcessorInterface;
-use Symfony\Component\HttpFoundation\Request;
-
-/**
- * Path processor to maintain BC for entity REST resource URLs from Drupal 8.0.
- */
-class PathProcessorEntityResourceBC implements InboundPathProcessorInterface {
-
-  /**
-   * The entity type manager.
-   *
-   * @var \Drupal\Core\Entity\EntityTypeManagerInterface
-   */
-  protected $entityTypeManager;
-
-  /**
-   * Creates a new PathProcessorEntityResourceBC instance.
-   *
-   * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
-   *   The entity type manager.
-   */
-  public function __construct(EntityTypeManagerInterface $entity_type_manager) {
-    $this->entityTypeManager = $entity_type_manager;
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public function processInbound($path, Request $request) {
-    if ($request->getMethod() === 'POST' && strpos($path, '/entity/') === 0) {
-      $parts = explode('/', $path);
-      $entity_type_id = array_pop($parts);
-
-      // Until Drupal 8.3, no entity types specified a link template for the
-      // 'create' link relation type. As of Drupal 8.3, all core content entity
-      // types provide this link relation type. This inbound path processor
-      // provides automatic backwards compatibility: it allows both the old
-      // default from \Drupal\rest\Plugin\rest\resource\EntityResource, i.e.
-      // "/entity/{entity_type}" and the link template specified in a particular
-      // entity type. The former is rewritten to the latter
-      // specific one if it exists.
-      $entity_type = $this->entityTypeManager->getDefinition($entity_type_id);
-      if ($entity_type->hasLinkTemplate('create')) {
-        return $entity_type->getLinkTemplate('create');
-      }
-    }
-    return $path;
-  }
-
-}
diff --git a/core/modules/rest/src/Plugin/ResourceBase.php b/core/modules/rest/src/Plugin/ResourceBase.php
index b40a031..2be0aac 100644
--- a/core/modules/rest/src/Plugin/ResourceBase.php
+++ b/core/modules/rest/src/Plugin/ResourceBase.php
@@ -101,14 +101,6 @@ public function routes() {
     $definition = $this->getPluginDefinition();
     $canonical_path = isset($definition['uri_paths']['canonical']) ? $definition['uri_paths']['canonical'] : '/' . strtr($this->pluginId, ':', '/') . '/{id}';
     $create_path = isset($definition['uri_paths']['create']) ? $definition['uri_paths']['create'] : '/' . strtr($this->pluginId, ':', '/');
-    // BC: the REST module originally created the POST URL for a resource by
-    // reading the 'https://www.drupal.org/link-relations/create' URI path from
-    // the plugin annotation. For consistency with entity type definitions, that
-    // then changed to reading the 'create' URI path. For any REST Resource
-    // plugins that were using the old mechanism, we continue to support that.
-    if (!isset($definition['uri_paths']['create']) && isset($definition['uri_paths']['https://www.drupal.org/link-relations/create'])) {
-      $create_path = $definition['uri_paths']['https://www.drupal.org/link-relations/create'];
-    }
 
     $route_name = strtr($this->pluginId, ':', '.');
 
diff --git a/core/modules/rest/src/Plugin/rest/resource/EntityResource.php b/core/modules/rest/src/Plugin/rest/resource/EntityResource.php
index 5d9849d..2eb663b 100644
--- a/core/modules/rest/src/Plugin/rest/resource/EntityResource.php
+++ b/core/modules/rest/src/Plugin/rest/resource/EntityResource.php
@@ -362,15 +362,7 @@ protected function generateFallbackAccessDeniedMessage(EntityInterface $entity,
    * {@inheritdoc}
    */
   public function permissions() {
-    // @see https://www.drupal.org/node/2664780
-    if ($this->configFactory->get('rest.settings')->get('bc_entity_resource_permissions')) {
-      // The default Drupal 8.0.x and 8.1.x behavior.
-      return parent::permissions();
-    }
-    else {
-      // The default Drupal 8.2.x behavior.
-      return [];
-    }
+    return [];
   }
 
   /**
diff --git a/core/modules/rest/src/RestServiceProvider.php b/core/modules/rest/src/RestServiceProvider.php
deleted file mode 100644
index e705de4..0000000
--- a/core/modules/rest/src/RestServiceProvider.php
+++ /dev/null
@@ -1,51 +0,0 @@
-<?php
-
-namespace Drupal\rest;
-
-use Drupal\Core\DependencyInjection\ContainerBuilder;
-use Drupal\Core\DependencyInjection\ServiceProviderInterface;
-use Drupal\rest\LinkManager\LinkManager;
-use Drupal\rest\LinkManager\RelationLinkManager;
-use Drupal\rest\LinkManager\TypeLinkManager;
-use Symfony\Component\DependencyInjection\DefinitionDecorator;
-use Symfony\Component\DependencyInjection\Reference;
-
-/**
- * Provides BC services.
- *
- * These services are not added via rest.services.yml because the service
- * classes extend classes from the HAL module. They also have no use without
- * that module.
- */
-class RestServiceProvider implements ServiceProviderInterface {
-
-  /**
-   * {@inheritdoc}
-   */
-  public function register(ContainerBuilder $container) {
-    $modules = $container->getParameter(('container.modules'));
-    if (isset($modules['hal'])) {
-      // @deprecated in Drupal 8.3.x and will be removed before Drupal 9.0.0.
-      //   Use hal.link_manager instead.
-      // @see https://www.drupal.org/node/2830467
-      $service_definition = new DefinitionDecorator(new Reference('hal.link_manager'));
-      $service_definition->setClass(LinkManager::class);
-      $container->setDefinition('rest.link_manager', $service_definition);
-
-      // @deprecated in Drupal 8.3.x and will be removed before Drupal 9.0.0.
-      //   Use hal.link_manager.type instead.
-      // @see https://www.drupal.org/node/2830467
-      $service_definition = new DefinitionDecorator(new Reference('hal.link_manager.type'));
-      $service_definition->setClass(TypeLinkManager::class);
-      $container->setDefinition('rest.link_manager.type', $service_definition);
-
-      // @deprecated in Drupal 8.3.x and will be removed before Drupal 9.0.0.
-      //   Use hal.link_manager.relation instead.
-      // @see https://www.drupal.org/node/2830467
-      $service_definition = new DefinitionDecorator(new Reference('hal.link_manager.relation'));
-      $service_definition->setClass(RelationLinkManager::class);
-      $container->setDefinition('rest.link_manager.relation', $service_definition);
-    }
-  }
-
-}
diff --git a/core/modules/rest/src/Tests/RESTTestBase.php b/core/modules/rest/src/Tests/RESTTestBase.php
deleted file mode 100644
index 40a9fe2..0000000
--- a/core/modules/rest/src/Tests/RESTTestBase.php
+++ /dev/null
@@ -1,624 +0,0 @@
-<?php
-
-namespace Drupal\rest\Tests;
-
-use Drupal\Component\Utility\NestedArray;
-use Drupal\Core\Config\Entity\ConfigEntityType;
-use Drupal\node\NodeInterface;
-use Drupal\rest\RestResourceConfigInterface;
-use Drupal\simpletest\WebTestBase;
-use GuzzleHttp\Cookie\FileCookieJar;
-use GuzzleHttp\Cookie\SetCookie;
-
-/**
- * Test helper class that provides a REST client method to send HTTP requests.
- *
- * @deprecated in Drupal 8.3.x-dev and will be removed before Drupal 9.0.0. Use \Drupal\Tests\rest\Functional\ResourceTestBase and \Drupal\Tests\rest\Functional\EntityResource\EntityResourceTestBase instead. Only retained for contributed module tests that may be using this base class.
- */
-abstract class RESTTestBase extends WebTestBase {
-
-  /**
-   * The REST resource config storage.
-   *
-   * @var \Drupal\Core\Entity\EntityStorageInterface
-   */
-  protected $resourceConfigStorage;
-
-  /**
-   * The default serialization format to use for testing REST operations.
-   *
-   * @var string
-   */
-  protected $defaultFormat;
-
-  /**
-   * The default MIME type to use for testing REST operations.
-   *
-   * @var string
-   */
-  protected $defaultMimeType;
-
-  /**
-   * The entity type to use for testing.
-   *
-   * @var string
-   */
-  protected $testEntityType = 'entity_test';
-
-  /**
-   * The default authentication provider to use for testing REST operations.
-   *
-   * @var array
-   */
-  protected $defaultAuth;
-
-
-  /**
-   * The raw response body from http request operations.
-   *
-   * @var array
-   */
-  protected $responseBody;
-
-  /**
-   * Modules to install.
-   *
-   * @var array
-   */
-  public static $modules = ['rest', 'entity_test'];
-
-  /**
-   * The last response.
-   *
-   * @var \Psr\Http\Message\ResponseInterface
-   */
-  protected $response;
-
-  protected function setUp() {
-    parent::setUp();
-    $this->defaultFormat = 'hal_json';
-    $this->defaultMimeType = 'application/hal+json';
-    $this->defaultAuth = ['cookie'];
-    $this->resourceConfigStorage = $this->container->get('entity_type.manager')->getStorage('rest_resource_config');
-    // Create a test content type for node testing.
-    if (in_array('node', static::$modules)) {
-      $this->drupalCreateContentType(['name' => 'resttest', 'type' => 'resttest']);
-    }
-
-    $this->cookieFile = $this->publicFilesDirectory . '/cookie.jar';
-  }
-
-  /**
-   * Calculates cookies used by guzzle later.
-   *
-   * @return \GuzzleHttp\Cookie\CookieJarInterface
-   *   The used CURL options in guzzle.
-   */
-  protected function cookies() {
-    $cookies = [];
-
-    foreach ($this->cookies as $key => $cookie) {
-      $cookies[$key][] = $cookie['value'];
-    }
-
-    $request = \Drupal::request();
-    $cookies = NestedArray::mergeDeep($cookies, $this->extractCookiesFromRequest($request));
-
-    $cookie_jar = new FileCookieJar($this->cookieFile);
-    foreach ($cookies as $key => $cookie_values) {
-      foreach ($cookie_values as $cookie_value) {
-        // setcookie() sets the value of a cookie to be deleted, when its gonna
-        // be removed.
-        if ($cookie_value !== 'deleted') {
-          $cookie_jar->setCookie(new SetCookie(['Name' => $key, 'Value' => $cookie_value, 'Domain' => $request->getHost()]));
-        }
-      }
-    }
-
-    return $cookie_jar;
-  }
-
-  /**
-   * Helper function to issue a HTTP request with simpletest's cURL.
-   *
-   * @param string|\Drupal\Core\Url $url
-   *   A Url object or system path.
-   * @param string $method
-   *   HTTP method, one of GET, POST, PUT or DELETE.
-   * @param string $body
-   *   The body for POST and PUT.
-   * @param string $mime_type
-   *   The MIME type of the transmitted content.
-   * @param bool $csrf_token
-   *   If NULL, a CSRF token will be retrieved and used. If FALSE, omit the
-   *   X-CSRF-Token request header (to simulate developer error). Otherwise, the
-   *   passed in value will be used as the value for the X-CSRF-Token request
-   *   header (to simulate developer error, by sending an invalid CSRF token).
-   *
-   * @return string
-   *   The content returned from the request.
-   */
-  protected function httpRequest($url, $method, $body = NULL, $mime_type = NULL, $csrf_token = NULL) {
-    if (!isset($mime_type)) {
-      $mime_type = $this->defaultMimeType;
-    }
-    if (!in_array($method, ['GET', 'HEAD', 'OPTIONS', 'TRACE'])) {
-      // GET the CSRF token first for writing requests.
-      $requested_token = $this->drupalGet('session/token');
-    }
-
-    $client = \Drupal::httpClient();
-    $url = $this->buildUrl($url);
-
-    $options = [
-      'http_errors' => FALSE,
-      'cookies' => $this->cookies(),
-      'curl' => [
-        CURLOPT_HEADERFUNCTION => [&$this, 'curlHeaderCallback'],
-      ],
-    ];
-    switch ($method) {
-      case 'GET':
-        $options += [
-          'headers' => [
-            'Accept' => $mime_type,
-          ],
-        ];
-        $response = $client->get($url, $options);
-        break;
-
-      case 'HEAD':
-        $response = $client->head($url, $options);
-        break;
-
-      case 'POST':
-        $options += [
-          'headers' => $csrf_token !== FALSE ? [
-            'Content-Type' => $mime_type,
-            'X-CSRF-Token' => ($csrf_token === NULL ? $requested_token : $csrf_token),
-          ] : [
-            'Content-Type' => $mime_type,
-          ],
-          'body' => $body,
-        ];
-        $response = $client->post($url, $options);
-        break;
-
-      case 'PUT':
-        $options += [
-          'headers' => $csrf_token !== FALSE ? [
-            'Content-Type' => $mime_type,
-            'X-CSRF-Token' => ($csrf_token === NULL ? $requested_token : $csrf_token),
-          ] : [
-            'Content-Type' => $mime_type,
-          ],
-          'body' => $body,
-        ];
-        $response = $client->put($url, $options);
-        break;
-
-      case 'PATCH':
-        $options += [
-          'headers' => $csrf_token !== FALSE ? [
-            'Content-Type' => $mime_type,
-            'X-CSRF-Token' => ($csrf_token === NULL ? $requested_token : $csrf_token),
-          ] : [
-            'Content-Type' => $mime_type,
-          ],
-          'body' => $body,
-        ];
-        $response = $client->patch($url, $options);
-        break;
-
-      case 'DELETE':
-        $options += [
-          'headers' => $csrf_token !== FALSE ? [
-            'Content-Type' => $mime_type,
-            'X-CSRF-Token' => ($csrf_token === NULL ? $requested_token : $csrf_token),
-          ] : [],
-        ];
-        $response = $client->delete($url, $options);
-        break;
-    }
-
-    $this->response = $response;
-    $this->responseBody = (string) $response->getBody();
-    $this->setRawContent($this->responseBody);
-
-    // Ensure that any changes to variables in the other thread are picked up.
-    $this->refreshVariables();
-
-    $this->verbose($method . ' request to: ' . $url .
-      '<hr />Code: ' . $this->response->getStatusCode() .
-      (isset($options['headers']) ? '<hr />Request headers: ' . nl2br(print_r($options['headers'], TRUE)) : '') .
-      (isset($options['body']) ? '<hr />Request body: ' . nl2br(print_r($options['body'], TRUE)) : '') .
-      '<hr />Response headers: ' . nl2br(print_r($response->getHeaders(), TRUE)) .
-      '<hr />Response body: ' . $this->responseBody);
-
-    return $this->responseBody;
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function assertResponse($code, $message = '', $group = 'Browser') {
-    if (!isset($this->response)) {
-      return parent::assertResponse($code, $message, $group);
-    }
-    return $this->assertEqual($code, $this->response->getStatusCode(), $message ? $message : "HTTP response expected $code, actual {$this->response->getStatusCode()}", $group);
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function drupalGetHeaders($all_requests = FALSE) {
-    if (!isset($this->response)) {
-      return parent::drupalGetHeaders($all_requests);
-    }
-    $lowercased_keys = array_map('strtolower', array_keys($this->response->getHeaders()));
-    return array_map(function (array $header) {
-      return implode(', ', $header);
-    }, array_combine($lowercased_keys, array_values($this->response->getHeaders())));
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function drupalGetHeader($name, $all_requests = FALSE) {
-    if (!isset($this->response)) {
-      return parent::drupalGetHeader($name, $all_requests);
-    }
-    if ($header = $this->response->getHeader($name)) {
-      return implode(', ', $header);
-    }
-  }
-
-  /**
-   * Creates entity objects based on their types.
-   *
-   * @param string $entity_type
-   *   The type of the entity that should be created.
-   *
-   * @return \Drupal\Core\Entity\EntityInterface
-   *   The new entity object.
-   */
-  protected function entityCreate($entity_type) {
-    return $this->container->get('entity_type.manager')
-      ->getStorage($entity_type)
-      ->create($this->entityValues($entity_type));
-  }
-
-  /**
-   * Provides an array of suitable property values for an entity type.
-   *
-   * Required properties differ from entity type to entity type, so we keep a
-   * minimum mapping here.
-   *
-   * @param string $entity_type_id
-   *   The ID of the type of entity that should be created.
-   *
-   * @return array
-   *   An array of values keyed by property name.
-   */
-  protected function entityValues($entity_type_id) {
-    switch ($entity_type_id) {
-      case 'entity_test':
-        return [
-          'name' => $this->randomMachineName(),
-          'user_id' => 1,
-          'field_test_text' => [0 => [
-            'value' => $this->randomString(),
-            'format' => 'plain_text',
-          ]],
-        ];
-      case 'config_test':
-        return [
-          'id' => $this->randomMachineName(),
-          'label' => 'Test label',
-        ];
-      case 'node':
-        return ['title' => $this->randomString(), 'type' => 'resttest'];
-      case 'node_type':
-        return [
-          'type' => 'article',
-          'name' => $this->randomMachineName(),
-        ];
-      case 'user':
-        return ['name' => $this->randomMachineName()];
-
-      case 'comment':
-        return [
-          'subject' => $this->randomMachineName(),
-          'entity_type' => 'node',
-          'comment_type' => 'comment',
-          'comment_body' => $this->randomString(),
-          'entity_id' => 'invalid',
-          'field_name' => 'comment',
-        ];
-      case 'taxonomy_vocabulary':
-        return [
-          'vid' => 'tags',
-          'name' => $this->randomMachineName(),
-        ];
-      case 'block':
-        // Block placements depend on themes, ensure Bartik is installed.
-        $this->container->get('theme_installer')->install(['bartik']);
-        return [
-          'id' => strtolower($this->randomMachineName(8)),
-          'plugin' => 'system_powered_by_block',
-          'theme' => 'bartik',
-          'region' => 'header',
-        ];
-      default:
-        if ($this->isConfigEntity($entity_type_id)) {
-          return $this->configEntityValues($entity_type_id);
-        }
-        return [];
-    }
-  }
-
-  /**
-   * Enables the REST service interface for a specific entity type.
-   *
-   * @param string|false $resource_type
-   *   The resource type that should get REST API enabled or FALSE to disable all
-   *   resource types.
-   * @param string $method
-   *   The HTTP method to enable, e.g. GET, POST etc.
-   * @param string|array $format
-   *   (Optional) The serialization format, e.g. hal_json, or a list of formats.
-   * @param array $auth
-   *   (Optional) The list of valid authentication methods.
-   */
-  protected function enableService($resource_type, $method = 'GET', $format = NULL, array $auth = []) {
-    if ($resource_type) {
-      // Enable REST API for this entity type.
-      $resource_config_id = str_replace(':', '.', $resource_type);
-      // get entity by id
-      /** @var \Drupal\rest\RestResourceConfigInterface $resource_config */
-      $resource_config = $this->resourceConfigStorage->load($resource_config_id);
-      if (!$resource_config) {
-        $resource_config = $this->resourceConfigStorage->create([
-          'id' => $resource_config_id,
-          'granularity' => RestResourceConfigInterface::METHOD_GRANULARITY,
-          'configuration' => []
-        ]);
-      }
-      $configuration = $resource_config->get('configuration');
-
-      if (is_array($format)) {
-        for ($i = 0; $i < count($format); $i++) {
-          $configuration[$method]['supported_formats'][] = $format[$i];
-        }
-      }
-      else {
-        if ($format == NULL) {
-          $format = $this->defaultFormat;
-        }
-        $configuration[$method]['supported_formats'][] = $format;
-      }
-
-      if (!is_array($auth) || empty($auth)) {
-        $auth = $this->defaultAuth;
-      }
-      foreach ($auth as $auth_provider) {
-        $configuration[$method]['supported_auth'][] = $auth_provider;
-      }
-
-      $resource_config->set('configuration', $configuration);
-      $resource_config->save();
-    }
-    else {
-      foreach ($this->resourceConfigStorage->loadMultiple() as $resource_config) {
-        $resource_config->delete();
-      }
-    }
-    $this->rebuildCache();
-  }
-
-  /**
-   * Rebuilds routing caches.
-   */
-  protected function rebuildCache() {
-    $this->container->get('router.builder')->rebuildIfNeeded();
-  }
-
-  /**
-   * {@inheritdoc}
-   *
-   * This method is overridden to deal with a cURL quirk: the usage of
-   * CURLOPT_CUSTOMREQUEST cannot be unset on the cURL handle, so we need to
-   * override it every time it is omitted.
-   */
-  protected function curlExec($curl_options, $redirect = FALSE) {
-    unset($this->response);
-
-    if (!isset($curl_options[CURLOPT_CUSTOMREQUEST])) {
-      if (!empty($curl_options[CURLOPT_HTTPGET])) {
-        $curl_options[CURLOPT_CUSTOMREQUEST] = 'GET';
-      }
-      if (!empty($curl_options[CURLOPT_POST])) {
-        $curl_options[CURLOPT_CUSTOMREQUEST] = 'POST';
-      }
-    }
-    return parent::curlExec($curl_options, $redirect);
-  }
-
-  /**
-   * Provides the necessary user permissions for entity operations.
-   *
-   * @param string $entity_type_id
-   *   The entity type.
-   * @param string $operation
-   *   The operation, one of 'view', 'create', 'update' or 'delete'.
-   *
-   * @return array
-   *   The set of user permission strings.
-   */
-  protected function entityPermissions($entity_type_id, $operation) {
-    switch ($entity_type_id) {
-      case 'entity_test':
-        switch ($operation) {
-          case 'view':
-            return ['view test entity'];
-          case 'create':
-          case 'update':
-          case 'delete':
-            return ['administer entity_test content'];
-        }
-      case 'node':
-        switch ($operation) {
-          case 'view':
-            return ['access content'];
-          case 'create':
-            return ['create resttest content'];
-          case 'update':
-            return ['edit any resttest content'];
-          case 'delete':
-            return ['delete any resttest content'];
-        }
-
-      case 'comment':
-        switch ($operation) {
-          case 'view':
-            return ['access comments'];
-
-          case 'create':
-            return ['post comments', 'skip comment approval'];
-
-          case 'update':
-            return ['edit own comments'];
-
-          case 'delete':
-            return ['administer comments'];
-        }
-        break;
-
-      case 'user':
-        switch ($operation) {
-          case 'view':
-            return ['access user profiles'];
-
-          default:
-            return ['administer users'];
-        }
-
-      default:
-        if ($this->isConfigEntity($entity_type_id)) {
-          $entity_type = \Drupal::entityTypeManager()->getDefinition($entity_type_id);
-          if ($admin_permission = $entity_type->getAdminPermission()) {
-            return [$admin_permission];
-          }
-        }
-    }
-    return [];
-  }
-
-  /**
-   * Loads an entity based on the location URL returned in the location header.
-   *
-   * @param string $location_url
-   *   The URL returned in the Location header.
-   *
-   * @return \Drupal\Core\Entity\Entity|false
-   *   The entity or FALSE if there is no matching entity.
-   */
-  protected function loadEntityFromLocationHeader($location_url) {
-    $url_parts = explode('/', $location_url);
-    $id = end($url_parts);
-    return $this->container->get('entity_type.manager')
-      ->getStorage($this->testEntityType)->load($id);
-  }
-
-  /**
-   * Remove node fields that can only be written by an admin user.
-   *
-   * @param \Drupal\node\NodeInterface $node
-   *   The node to remove fields where non-administrative users cannot write.
-   *
-   * @return \Drupal\node\NodeInterface
-   *   The node with removed fields.
-   */
-  protected function removeNodeFieldsForNonAdminUsers(NodeInterface $node) {
-    $node->set('status', NULL);
-    $node->set('created', NULL);
-    $node->set('changed', NULL);
-    $node->set('promote', NULL);
-    $node->set('sticky', NULL);
-    $node->set('revision_timestamp', NULL);
-    $node->set('revision_log', NULL);
-    $node->set('uid', NULL);
-
-    return $node;
-  }
-
-  /**
-   * Check to see if the HTTP request response body is identical to the expected
-   * value.
-   *
-   * @param $expected
-   *   The first value to check.
-   * @param $message
-   *   (optional) A message to display with the assertion. Do not translate
-   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
-   *   variables in the message text, not t(). If left blank, a default message
-   *   will be displayed.
-   * @param $group
-   *   (optional) The group this message is in, which is displayed in a column
-   *   in test output. Use 'Debug' to indicate this is debugging output. Do not
-   *   translate this string. Defaults to 'Other'; most tests do not override
-   *   this default.
-   *
-   * @return bool
-   *   TRUE if the assertion succeeded, FALSE otherwise.
-   */
-  protected function assertResponseBody($expected, $message = '', $group = 'REST Response') {
-    return $this->assertIdentical($expected, $this->responseBody, $message ? $message : strtr('Response body @expected (expected) is equal to @response (actual).', ['@expected' => var_export($expected, TRUE), '@response' => var_export($this->responseBody, TRUE)]), $group);
-  }
-
-  /**
-   * Checks if an entity type id is for a Config Entity.
-   *
-   * @param string $entity_type_id
-   *   The entity type ID to check.
-   *
-   * @return bool
-   *   TRUE if the entity is a Config Entity, FALSE otherwise.
-   */
-  protected function isConfigEntity($entity_type_id) {
-    return \Drupal::entityTypeManager()->getDefinition($entity_type_id) instanceof ConfigEntityType;
-  }
-
-  /**
-   * Provides an array of suitable property values for a config entity type.
-   *
-   * Config entities have some common keys that need to be created. Required
-   * properties differ among config entity types, so we keep a minimum mapping
-   * here.
-   *
-   * @param string $entity_type_id
-   *   The ID of the type of entity that should be created.
-   *
-   * @return array
-   *   An array of values keyed by property name.
-   */
-  protected function configEntityValues($entity_type_id) {
-    $entity_type = \Drupal::entityTypeManager()->getDefinition($entity_type_id);
-    $keys = $entity_type->getKeys();
-    $values = [];
-    // Fill out known key values that are shared across entity types.
-    foreach ($keys as $key) {
-      if ($key === 'id' || $key === 'label') {
-        $values[$key] = $this->randomMachineName();
-      }
-    }
-    // Add extra values for particular entity types.
-    switch ($entity_type_id) {
-      case 'block':
-        $values['plugin'] = 'system_powered_by_block';
-        break;
-    }
-    return $values;
-  }
-
-}
diff --git a/core/modules/rest/tests/fixtures/update/drupal-8.rest-rest_post_update_resource_granularity.php b/core/modules/rest/tests/fixtures/update/drupal-8.rest-rest_post_update_resource_granularity.php
deleted file mode 100644
index aa94c63..0000000
Binary files a/core/modules/rest/tests/fixtures/update/drupal-8.rest-rest_post_update_resource_granularity.php and /dev/null differ
diff --git a/core/modules/rest/tests/fixtures/update/drupal-8.rest-rest_update_8201.php b/core/modules/rest/tests/fixtures/update/drupal-8.rest-rest_update_8201.php
deleted file mode 100644
index 17a69d5..0000000
--- a/core/modules/rest/tests/fixtures/update/drupal-8.rest-rest_update_8201.php
+++ /dev/null
@@ -1,59 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains database additions to drupal-8.bare.standard.php.gz for testing the
- * upgrade path of rest_update_8201().
- */
-
-use Drupal\Core\Database\Database;
-
-$connection = Database::getConnection();
-
-// Set the schema version.
-$connection->insert('key_value')
-  ->fields([
-    'collection' => 'system.schema',
-    'name' => 'rest',
-    'value' => 'i:8000;',
-  ])
-  ->execute();
-
-// Update core.extension.
-$extensions = $connection->select('config')
-  ->fields('config', ['data'])
-  ->condition('collection', '')
-  ->condition('name', 'core.extension')
-  ->execute()
-  ->fetchField();
-$extensions = unserialize($extensions);
-$extensions['module']['basic_auth'] = 0;
-$extensions['module']['rest'] = 0;
-$extensions['module']['serialization'] = 0;
-$connection->update('config')
-  ->fields([
-    'data' => serialize($extensions),
-  ])
-  ->condition('collection', '')
-  ->condition('name', 'core.extension')
-  ->execute();
-
-// Install the rest configuration.
-$config = [
-  'resources' => [
-    'entity:node' => [
-      'GET' => [
-        'supported_formats' => ['json'],
-        'supported_auth' => ['basic_auth'],
-      ],
-    ],
-  ],
-  'link_domain' => NULL,
-];
-$data = $connection->insert('config')
-  ->fields([
-    'name' => 'rest.settings',
-    'data' => serialize($config),
-    'collection' => ''
-  ])
-  ->execute();
diff --git a/core/modules/rest/tests/fixtures/update/drupal-8.rest-rest_update_8203.php b/core/modules/rest/tests/fixtures/update/drupal-8.rest-rest_update_8203.php
deleted file mode 100644
index 15acff9..0000000
--- a/core/modules/rest/tests/fixtures/update/drupal-8.rest-rest_update_8203.php
+++ /dev/null
@@ -1,58 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains database additions to drupal-8.bare.standard.php.gz for testing the
- * upgrade path of rest_update_8203().
- */
-
-use Drupal\Core\Database\Database;
-
-$connection = Database::getConnection();
-
-// Set the schema version.
-$connection->insert('key_value')
-  ->fields([
-    'collection' => 'system.schema',
-    'name' => 'rest',
-    'value' => 'i:8000;',
-  ])
-  ->execute();
-
-// Update core.extension.
-$extensions = $connection->select('config')
-  ->fields('config', ['data'])
-  ->condition('collection', '')
-  ->condition('name', 'core.extension')
-  ->execute()
-  ->fetchField();
-$extensions = unserialize($extensions);
-$extensions['module']['rest'] = 0;
-$extensions['module']['serialization'] = 0;
-$connection->update('config')
-  ->fields([
-    'data' => serialize($extensions),
-  ])
-  ->condition('collection', '')
-  ->condition('name', 'core.extension')
-  ->execute();
-
-// Install the rest configuration.
-$config = [
-  'resources' => [
-    'entity:node' => [
-      'GET' => [
-        'supported_formats' => ['json'],
-        'supported_auth' => ['basic_auth'],
-      ],
-    ],
-  ],
-  'link_domain' => NULL,
-];
-$data = $connection->insert('config')
-  ->fields([
-    'name' => 'rest.settings',
-    'data' => serialize($config),
-    'collection' => ''
-  ])
-  ->execute();
diff --git a/core/modules/rest/tests/fixtures/update/rest-export-with-authentication.php b/core/modules/rest/tests/fixtures/update/rest-export-with-authentication.php
deleted file mode 100644
index 7d72d49..0000000
--- a/core/modules/rest/tests/fixtures/update/rest-export-with-authentication.php
+++ /dev/null
@@ -1,65 +0,0 @@
-<?php
-
-/**
- * @file
- * Test fixture for \Drupal\rest\Tests\Update\RestExportAuthUpdateTest.
- */
-
-use Drupal\Core\Database\Database;
-use Drupal\Core\Serialization\Yaml;
-
-$connection = Database::getConnection();
-$config = $connection;
-
-// Set the schema version.
-$connection->insert('key_value')
-  ->fields([
-    'collection' => 'system.schema',
-    'name' => 'rest',
-    'value' => 'i:8000;',
-  ])
-  ->execute();
-
-// Update core.extension.
-$extensions = $connection->select('config')
-  ->fields('config', ['data'])
-  ->condition('collection', '')
-  ->condition('name', 'core.extension')
-  ->execute()
-  ->fetchField();
-$extensions = unserialize($extensions);
-$extensions['module']['rest'] = 0;
-$extensions['module']['serialization'] = 0;
-$extensions['module']['basic_auth'] = 0;
-$connection->update('config')
-  ->fields([
-    'data' => serialize($extensions),
-  ])
-  ->condition('collection', '')
-  ->condition('name', 'core.extension')
-  ->execute();
-
-$config = [
-  'link_domain' => '~',
-];
-$data = $connection->insert('config')
-  ->fields([
-    'name' => 'rest.settings',
-    'data' => serialize($config),
-    'collection' => '',
-  ])
-  ->execute();
-
-$connection->insert('config')
-  ->fields([
-    'name' => 'views.view.rest_export_with_authorization',
-  ])
-  ->execute();
-
-$connection->merge('config')
-  ->condition('name', 'views.view.rest_export_with_authorization')
-  ->condition('collection', '')
-  ->fields([
-    'data' => serialize(Yaml::decode(file_get_contents('core/modules/views/tests/modules/views_test_config/test_views/views.view.rest_export_with_authorization.yml'))),
-  ])
-  ->execute();
diff --git a/core/modules/rest/tests/fixtures/update/rest.resource.entity.comment_2721595.yml b/core/modules/rest/tests/fixtures/update/rest.resource.entity.comment_2721595.yml
deleted file mode 100644
index 7e86bab..0000000
--- a/core/modules/rest/tests/fixtures/update/rest.resource.entity.comment_2721595.yml
+++ /dev/null
@@ -1,32 +0,0 @@
-id: entity.comment
-plugin_id: 'entity:comment'
-granularity: method
-configuration:
-  GET:
-    supported_formats:
-      - hal_json
-      # This resource has a method-specific format.
-      # @see \Drupal\rest\Tests\Update\ResourceGranularityUpdateTest
-      - xml
-    supported_auth:
-      - basic_auth
-  POST:
-    supported_formats:
-      - hal_json
-    supported_auth:
-      - basic_auth
-  PATCH:
-    supported_formats:
-      - hal_json
-    supported_auth:
-      - basic_auth
-  DELETE:
-    supported_formats:
-      - hal_json
-    supported_auth:
-      - basic_auth
-dependencies:
-  module:
-    - node
-    - basic_auth
-    - hal
diff --git a/core/modules/rest/tests/fixtures/update/rest.resource.entity.node_2721595.yml b/core/modules/rest/tests/fixtures/update/rest.resource.entity.node_2721595.yml
deleted file mode 100644
index 0cf4d78..0000000
--- a/core/modules/rest/tests/fixtures/update/rest.resource.entity.node_2721595.yml
+++ /dev/null
@@ -1,29 +0,0 @@
-id: entity.node
-plugin_id: 'entity:node'
-granularity: method
-configuration:
-  GET:
-    supported_formats:
-      - hal_json
-    supported_auth:
-      - basic_auth
-  POST:
-    supported_formats:
-      - hal_json
-    supported_auth:
-      - basic_auth
-  PATCH:
-    supported_formats:
-      - hal_json
-    supported_auth:
-      - basic_auth
-  DELETE:
-    supported_formats:
-      - hal_json
-    supported_auth:
-      - basic_auth
-dependencies:
-  module:
-    - node
-    - basic_auth
-    - hal
diff --git a/core/modules/rest/tests/fixtures/update/rest.resource.entity.user_2721595.yml b/core/modules/rest/tests/fixtures/update/rest.resource.entity.user_2721595.yml
deleted file mode 100644
index 593a260..0000000
--- a/core/modules/rest/tests/fixtures/update/rest.resource.entity.user_2721595.yml
+++ /dev/null
@@ -1,32 +0,0 @@
-id: entity.user
-plugin_id: 'entity:user'
-granularity: method
-configuration:
-  GET:
-    supported_formats:
-      - hal_json
-    supported_auth:
-      - basic_auth
-      # This resource has a method-specific authentication.
-      # @see \Drupal\rest\Tests\Update\ResourceGranularityUpdateTest
-      - oauth
-  POST:
-    supported_formats:
-      - hal_json
-    supported_auth:
-      - basic_auth
-  PATCH:
-    supported_formats:
-      - hal_json
-    supported_auth:
-      - basic_auth
-  DELETE:
-    supported_formats:
-      - hal_json
-    supported_auth:
-      - basic_auth
-dependencies:
-  module:
-    - node
-    - basic_auth
-    - hal
diff --git a/core/modules/rest/tests/src/Functional/BcTimestampNormalizerUnixTestTrait.php b/core/modules/rest/tests/src/Functional/BcTimestampNormalizerUnixTestTrait.php
deleted file mode 100644
index a275f64..0000000
--- a/core/modules/rest/tests/src/Functional/BcTimestampNormalizerUnixTestTrait.php
+++ /dev/null
@@ -1,43 +0,0 @@
-<?php
-
-namespace Drupal\Tests\rest\Functional;
-
-/**
- * Trait for ResourceTestBase subclasses formatting expected timestamp data.
- */
-trait BcTimestampNormalizerUnixTestTrait {
-
-  /**
-   * Formats a UNIX timestamp.
-   *
-   * Depending on the 'bc_timestamp_normalizer_unix' setting. The return will be
-   * an RFC3339 date string or the same timestamp that was passed in.
-   *
-   * @param int $timestamp
-   *   The timestamp value to format.
-   *
-   * @return string|int
-   *   The formatted RFC3339 date string or UNIX timestamp.
-   *
-   * @see \Drupal\serialization\Normalizer\TimestampItemNormalizer
-   */
-  protected function formatExpectedTimestampItemValues($timestamp) {
-    // If the setting is enabled, just return the timestamp as-is now.
-    if ($this->config('serialization.settings')->get('bc_timestamp_normalizer_unix')) {
-      return ['value' => $timestamp];
-    }
-
-    // Otherwise, format the date string to the same that
-    // \Drupal\serialization\Normalizer\TimestampItemNormalizer will produce.
-    $date = new \DateTime();
-    $date->setTimestamp($timestamp);
-    $date->setTimezone(new \DateTimeZone('UTC'));
-
-    // Format is also added to the expected return values.
-    return [
-      'value' => $date->format(\DateTime::RFC3339),
-      'format' => \DateTime::RFC3339,
-    ];
-  }
-
-}
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/BaseFieldOverride/BaseFieldOverrideResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/BaseFieldOverride/BaseFieldOverrideResourceTestBase.php
index 1f4b03a..9725e34 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/BaseFieldOverride/BaseFieldOverrideResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/BaseFieldOverride/BaseFieldOverrideResourceTestBase.php
@@ -101,10 +101,6 @@ protected function getExpectedCacheContexts() {
    * {@inheritdoc}
    */
   protected function getExpectedUnauthorizedAccessMessage($method) {
-    if ($this->config('rest.settings')->get('bc_entity_resource_permissions')) {
-      return parent::getExpectedUnauthorizedAccessMessage($method);
-    }
-
     return "The 'administer node fields' permission is required.";
   }
 
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/Block/BlockResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/Block/BlockResourceTestBase.php
index d86f9b1..ee2cc64 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/Block/BlockResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/Block/BlockResourceTestBase.php
@@ -129,10 +129,6 @@ protected function getExpectedCacheTags() {
    * {@inheritdoc}
    */
   protected function getExpectedUnauthorizedAccessMessage($method) {
-    if ($this->config('rest.settings')->get('bc_entity_resource_permissions')) {
-      return parent::getExpectedUnauthorizedAccessMessage($method);
-    }
-
     switch ($method) {
       case 'GET':
         return "You are not authorized to view this block entity.";
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/Comment/CommentResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/Comment/CommentResourceTestBase.php
index 5b51014..cbd6075 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/Comment/CommentResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/Comment/CommentResourceTestBase.php
@@ -6,14 +6,13 @@
 use Drupal\comment\Entity\CommentType;
 use Drupal\comment\Tests\CommentTestTrait;
 use Drupal\entity_test\Entity\EntityTest;
-use Drupal\Tests\rest\Functional\BcTimestampNormalizerUnixTestTrait;
 use Drupal\Tests\rest\Functional\EntityResource\EntityResourceTestBase;
 use Drupal\user\Entity\User;
 use GuzzleHttp\RequestOptions;
 
 abstract class CommentResourceTestBase extends EntityResourceTestBase {
 
-  use CommentTestTrait, BcTimestampNormalizerUnixTestTrait;
+  use CommentTestTrait;
 
   /**
    * {@inheritdoc}
@@ -149,10 +148,16 @@ protected function getExpectedNormalizedEntity() {
         ],
       ],
       'created' => [
-        $this->formatExpectedTimestampItemValues(123456789),
+        [
+          'value' => (new \DateTime())->setTimestamp(123456789)->setTimezone(new \DateTimeZone('UTC'))->format(\DateTime::RFC3339),
+          'format' => \DateTime::RFC3339,
+        ],
       ],
       'changed' => [
-        $this->formatExpectedTimestampItemValues($this->entity->getChangedTime()),
+        [
+          'value' => (new \DateTime())->setTimestamp((int) $this->entity->getChangedTime())->setTimezone(new \DateTimeZone('UTC'))->format(\DateTime::RFC3339),
+          'format' => \DateTime::RFC3339,
+        ],
       ],
       'default_langcode' => [
         [
@@ -310,10 +315,6 @@ public function testPostDxWithoutCriticalBaseFields() {
    * {@inheritdoc}
    */
   protected function getExpectedUnauthorizedAccessMessage($method) {
-    if ($this->config('rest.settings')->get('bc_entity_resource_permissions')) {
-      return parent::getExpectedUnauthorizedAccessMessage($method);
-    }
-
     switch ($method) {
       case 'GET';
         return "The 'access comments' permission is required and the comment must be published.";
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/Editor/EditorResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/Editor/EditorResourceTestBase.php
index 4eb4a6e..4f20778 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/Editor/EditorResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/Editor/EditorResourceTestBase.php
@@ -174,10 +174,6 @@ protected function getExpectedCacheContexts() {
    * {@inheritdoc}
    */
   protected function getExpectedUnauthorizedAccessMessage($method) {
-    if ($this->config('rest.settings')->get('bc_entity_resource_permissions')) {
-      return parent::getExpectedUnauthorizedAccessMessage($method);
-    }
-
     return "The 'administer filters' permission is required.";
   }
 
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
index f39b7d8..2485d0c 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
@@ -228,11 +228,6 @@ protected function getNormalizedPatchEntity() {
    * {@inheritdoc}
    */
   protected function getExpectedUnauthorizedAccessMessage($method) {
-
-    if ($this->config('rest.settings')->get('bc_entity_resource_permissions')) {
-      return parent::getExpectedUnauthorizedAccessMessage($method);
-    }
-
     $permission = $this->entity->getEntityType()->getAdminPermission();
     if ($permission !== FALSE) {
       return "The '{$permission}' permission is required.";
@@ -497,91 +492,6 @@ public function testGet() {
     }
     $this->assertSame($get_headers, $head_headers);
 
-    // BC: serialization_update_8302().
-    // Only run this for fieldable entities. It doesn't make sense for config
-    // entities as config values are already casted. They also run through the
-    // ConfigEntityNormalizer, which doesn't deal with fields individually.
-    if ($this->entity instanceof FieldableEntityInterface) {
-      // Test primitive data casting BC (strings).
-      $this->config('serialization.settings')->set('bc_primitives_as_strings', TRUE)->save(TRUE);
-      // Rebuild the container so new config is reflected in the addition of the
-      // PrimitiveDataNormalizer.
-      $this->rebuildAll();
-
-
-      $response = $this->request('GET', $url, $request_options);
-      $this->assertResourceResponse(200, FALSE, $response);
-
-
-      // Again do an identical comparison, but this time transform the expected
-      // normalized entity's values to strings. This ensures the BC layer for
-      // bc_primitives_as_strings works as expected.
-      $expected = $this->getExpectedNormalizedEntity();
-      // Config entities are not affected.
-      // @see \Drupal\serialization\Normalizer\ConfigEntityNormalizer::normalize()
-      $expected = static::castToString($expected);
-      static::recursiveKSort($expected);
-      $actual = $this->serializer->decode((string) $response->getBody(), static::$format);
-      static::recursiveKSort($actual);
-      $this->assertSame($expected, $actual);
-
-      // Reset the config value and rebuild.
-      $this->config('serialization.settings')->set('bc_primitives_as_strings', FALSE)->save(TRUE);
-      $this->rebuildAll();
-    }
-
-    // BC: serialization_update_8401().
-    // Only run this for fieldable entities. It doesn't make sense for config
-    // entities as config values always use the raw values (as per the config
-    // schema), returned directly from the ConfigEntityNormalizer, which
-    // doesn't deal with fields individually.
-    if ($this->entity instanceof FieldableEntityInterface) {
-      // Test the BC settings for timestamp values.
-      $this->config('serialization.settings')->set('bc_timestamp_normalizer_unix', TRUE)->save(TRUE);
-      // Rebuild the container so new config is reflected in the addition of the
-      // TimestampItemNormalizer.
-      $this->rebuildAll();
-
-
-      $response = $this->request('GET', $url, $request_options);
-      $this->assertResourceResponse(200, FALSE, $response);
-
-
-      // This ensures the BC layer for bc_timestamp_normalizer_unix works as
-      // expected. This method should be using
-      // ::formatExpectedTimestampValue() to generate the timestamp value. This
-      // will take into account the above config setting.
-      $expected = $this->getExpectedNormalizedEntity();
-      // Config entities are not affected.
-      // @see \Drupal\serialization\Normalizer\ConfigEntityNormalizer::normalize()
-      static::recursiveKSort($expected);
-      $actual = $this->serializer->decode((string) $response->getBody(), static::$format);
-      static::recursiveKSort($actual);
-      $this->assertSame($expected, $actual);
-
-      // Reset the config value and rebuild.
-      $this->config('serialization.settings')->set('bc_timestamp_normalizer_unix', FALSE)->save(TRUE);
-      $this->rebuildAll();
-    }
-
-
-    // BC: rest_update_8203().
-    $this->config('rest.settings')->set('bc_entity_resource_permissions', TRUE)->save(TRUE);
-    $this->refreshTestStateAfterRestConfigChange();
-
-
-    // DX: 403 when unauthorized.
-    $response = $this->request('GET', $url, $request_options);
-    $this->assertResourceErrorResponse(403, $this->getExpectedUnauthorizedAccessMessage('GET'), $response);
-
-
-    $this->grantPermissionsToTestedRole(['restful get entity:' . static::$entityTypeId]);
-
-
-    // 200 for well-formed request.
-    $response = $this->request('GET', $url, $request_options);
-    $this->assertResourceResponse(200, FALSE, $response);
-
 
     $this->resourceConfigStorage->load(static::$resourceConfigId)->disable()->save();
     $this->refreshTestStateAfterRestConfigChange();
@@ -865,45 +775,6 @@ public function testPost() {
         $this->assertArraySubset(static::castToString($field_normalization), $created_entity->get($field_name)->getValue(), TRUE);
       }
     }
-
-
-    $this->config('rest.settings')->set('bc_entity_resource_permissions', TRUE)->save(TRUE);
-    $this->refreshTestStateAfterRestConfigChange();
-    $request_options[RequestOptions::BODY] = $parseable_valid_request_body_2;
-
-
-    // DX: 403 when unauthorized.
-    $response = $this->request('POST', $url, $request_options);
-    $this->assertResourceErrorResponse(403, $this->getExpectedUnauthorizedAccessMessage('POST'), $response);
-
-
-    $this->grantPermissionsToTestedRole(['restful post entity:' . static::$entityTypeId]);
-
-
-    // 201 for well-formed request.
-    // Delete the first created entity in case there is a uniqueness constraint.
-    $this->entityStorage->load(static::$firstCreatedEntityId)->delete();
-    $response = $this->request('POST', $url, $request_options);
-    $this->assertResourceResponse(201, FALSE, $response);
-    if ($has_canonical_url) {
-      $location = $this->entityStorage->load(static::$secondCreatedEntityId)->toUrl('canonical')->setAbsolute(TRUE)->toString();
-      $this->assertSame([$location], $response->getHeader('Location'));
-    }
-    else {
-      $this->assertSame([], $response->getHeader('Location'));
-    }
-    $this->assertFalse($response->hasHeader('X-Drupal-Cache'));
-
-    // BC: old default POST URLs have their path updated by the inbound path
-    // processor \Drupal\rest\PathProcessor\PathProcessorEntityResourceBC to the
-    // new URL, which is derived from the 'create' link template if an entity
-    // type specifies it.
-    if ($this->entity->getEntityType()->hasLinkTemplate('create')) {
-      $this->entityStorage->load(static::$secondCreatedEntityId)->delete();
-      $old_url = Url::fromUri('base:entity/' . static::$entityTypeId);
-      $response = $this->request('POST', $old_url, $request_options);
-      $this->assertResourceResponse(201, FALSE, $response);
-    }
   }
 
   /**
@@ -1099,25 +970,6 @@ public function testPatch() {
     // request. Test this using the configurable field that we added, but which
     // is not sent in the PATCH request.
     $this->assertSame('All the faith he had had had had no effect on the outcome of his life.', $updated_entity->get('field_rest_test')->value);
-
-
-    $this->config('rest.settings')->set('bc_entity_resource_permissions', TRUE)->save(TRUE);
-    $this->refreshTestStateAfterRestConfigChange();
-    $request_options[RequestOptions::BODY] = $parseable_valid_request_body_2;
-
-
-    // DX: 403 when unauthorized.
-    $response = $this->request('PATCH', $url, $request_options);
-    $this->assertResourceErrorResponse(403, $this->getExpectedUnauthorizedAccessMessage('PATCH'), $response);
-
-
-    $this->grantPermissionsToTestedRole(['restful patch entity:' . static::$entityTypeId]);
-
-
-    // 200 for well-formed request.
-    $response = $this->request('PATCH', $url, $request_options);
-    $this->assertResourceResponse(200, FALSE, $response);
-    $this->assertFalse($response->hasHeader('X-Drupal-Cache'));
   }
 
   /**
@@ -1207,29 +1059,6 @@ public function testDelete() {
     // $this->assertSame(FALSE, $response->hasHeader('Content-Type'));
     $this->assertSame('', (string) $response->getBody());
     $this->assertFalse($response->hasHeader('X-Drupal-Cache'));
-
-
-    $this->config('rest.settings')->set('bc_entity_resource_permissions', TRUE)->save(TRUE);
-    $this->refreshTestStateAfterRestConfigChange();
-    $this->entity = $this->createEntity();
-    $url = $this->getEntityResourceUrl()->setOption('query', $url->getOption('query'));
-
-
-    // DX: 403 when unauthorized.
-    $response = $this->request('DELETE', $url, $request_options);
-    $this->assertResourceErrorResponse(403, $this->getExpectedUnauthorizedAccessMessage('DELETE'), $response);
-
-
-    $this->grantPermissionsToTestedRole(['restful delete entity:' . static::$entityTypeId]);
-
-
-    // 204 for well-formed request.
-    $response = $this->request('DELETE', $url, $request_options);
-    $this->assertSame(204, $response->getStatusCode());
-    // @todo Uncomment the following line when https://www.drupal.org/node/2821711 is fixed.
-    // $this->assertSame(FALSE, $response->hasHeader('Content-Type'));
-    $this->assertSame('', (string) $response->getBody());
-    $this->assertFalse($response->hasHeader('X-Drupal-Cache'));
   }
 
   /**
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/EntityTest/EntityTestResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/EntityTest/EntityTestResourceTestBase.php
index e2c0ccd..09d9649 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/EntityTest/EntityTestResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/EntityTest/EntityTestResourceTestBase.php
@@ -3,14 +3,11 @@
 namespace Drupal\Tests\rest\Functional\EntityResource\EntityTest;
 
 use Drupal\entity_test\Entity\EntityTest;
-use Drupal\Tests\rest\Functional\BcTimestampNormalizerUnixTestTrait;
 use Drupal\Tests\rest\Functional\EntityResource\EntityResourceTestBase;
 use Drupal\user\Entity\User;
 
 abstract class EntityTestResourceTestBase extends EntityResourceTestBase {
 
-  use BcTimestampNormalizerUnixTestTrait;
-
   /**
    * {@inheritdoc}
    */
@@ -95,7 +92,10 @@ protected function getExpectedNormalizedEntity() {
         ]
       ],
       'created' => [
-        $this->formatExpectedTimestampItemValues((int) $this->entity->get('created')->value)
+        [
+          'value' => (new \DateTime())->setTimestamp((int) $this->entity->get('created')->value)->setTimezone(new \DateTimeZone('UTC'))->format(\DateTime::RFC3339),
+          'format' => \DateTime::RFC3339,
+        ],
       ],
       'user_id' => [
         [
@@ -133,10 +133,6 @@ protected function getNormalizedPostEntity() {
    * {@inheritdoc}
    */
   protected function getExpectedUnauthorizedAccessMessage($method) {
-    if ($this->config('rest.settings')->get('bc_entity_resource_permissions')) {
-      return parent::getExpectedUnauthorizedAccessMessage($method);
-    }
-
     switch ($method) {
       case 'GET':
         return "The 'view test entity' permission is required.";
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/EntityTestLabel/EntityTestLabelResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/EntityTestLabel/EntityTestLabelResourceTestBase.php
index 2257d6c..9ae5cc5 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/EntityTestLabel/EntityTestLabelResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/EntityTestLabel/EntityTestLabelResourceTestBase.php
@@ -3,14 +3,11 @@
 namespace Drupal\Tests\rest\Functional\EntityResource\EntityTestLabel;
 
 use Drupal\entity_test\Entity\EntityTestLabel;
-use Drupal\Tests\rest\Functional\BcTimestampNormalizerUnixTestTrait;
 use Drupal\Tests\rest\Functional\EntityResource\EntityResourceTestBase;
 use Drupal\user\Entity\User;
 
 abstract class EntityTestLabelResourceTestBase extends EntityResourceTestBase {
 
-  use BcTimestampNormalizerUnixTestTrait;
-
   /**
    * {@inheritdoc}
    */
@@ -97,7 +94,10 @@ protected function getExpectedNormalizedEntity() {
         ],
       ],
       'created' => [
-        $this->formatExpectedTimestampItemValues((int) $this->entity->get('created')->value),
+        [
+          'value' => (new \DateTime())->setTimestamp((int) $this->entity->get('created')->value)->setTimezone(new \DateTimeZone('UTC'))->format(\DateTime::RFC3339),
+          'format' => \DateTime::RFC3339,
+        ],
       ],
       'user_id' => [
         [
@@ -141,10 +141,6 @@ protected function getExpectedCacheContexts() {
    * {@inheritdoc}
    */
   protected function getExpectedUnauthorizedAccessMessage($method) {
-    if ($this->config('rest.settings')->get('bc_entity_resource_permissions')) {
-      return parent::getExpectedUnauthorizedAccessMessage($method);
-    }
-
     switch ($method) {
       case 'GET':
         return "The 'view test entity' permission is required.";
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/Feed/FeedResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/Feed/FeedResourceTestBase.php
index 1e79395..eda368d 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/Feed/FeedResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/Feed/FeedResourceTestBase.php
@@ -2,14 +2,11 @@
 
 namespace Drupal\Tests\rest\Functional\EntityResource\Feed;
 
-use Drupal\Tests\rest\Functional\BcTimestampNormalizerUnixTestTrait;
 use Drupal\Tests\rest\Functional\EntityResource\EntityTest\EntityTestResourceTestBase;
 use Drupal\aggregator\Entity\Feed;
 
 abstract class FeedResourceTestBase extends EntityTestResourceTestBase {
 
-  use BcTimestampNormalizerUnixTestTrait;
-
   /**
    * {@inheritdoc}
    */
@@ -95,10 +92,16 @@ protected function getExpectedNormalizedEntity() {
         ]
       ],
       'checked' => [
-        $this->formatExpectedTimestampItemValues(123456789),
+        [
+          'value' => (new \DateTime())->setTimestamp(123456789)->setTimezone(new \DateTimeZone('UTC'))->format(\DateTime::RFC3339),
+          'format' => \DateTime::RFC3339,
+        ],
       ],
       'queued' => [
-        $this->formatExpectedTimestampItemValues(123456789),
+        [
+          'value' => (new \DateTime())->setTimestamp(123456789)->setTimezone(new \DateTimeZone('UTC'))->format(\DateTime::RFC3339),
+          'format' => \DateTime::RFC3339,
+        ],
       ],
       'link' => [
         [
@@ -126,7 +129,10 @@ protected function getExpectedNormalizedEntity() {
         ]
       ],
       'modified' => [
-        $this->formatExpectedTimestampItemValues(123456789),
+        [
+          'value' => (new \DateTime())->setTimestamp(123456789)->setTimezone(new \DateTimeZone('UTC'))->format(\DateTime::RFC3339),
+          'format' => \DateTime::RFC3339,
+        ],
       ],
     ];
   }
@@ -163,10 +169,6 @@ protected function getNormalizedPostEntity() {
    * {@inheritdoc}
    */
   protected function getExpectedUnauthorizedAccessMessage($method) {
-    if ($this->config('rest.settings')->get('bc_entity_resource_permissions')) {
-      return parent::getExpectedUnauthorizedAccessMessage($method);
-    }
-
     switch ($method) {
       case 'GET':
         return "The 'access news feeds' permission is required.";
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/FieldConfig/FieldConfigResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/FieldConfig/FieldConfigResourceTestBase.php
index 05c05f4..fd82c7a 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/FieldConfig/FieldConfigResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/FieldConfig/FieldConfigResourceTestBase.php
@@ -109,10 +109,6 @@ protected function getExpectedCacheContexts() {
    * {@inheritdoc}
    */
   protected function getExpectedUnauthorizedAccessMessage($method) {
-    if ($this->config('rest.settings')->get('bc_entity_resource_permissions')) {
-      return parent::getExpectedUnauthorizedAccessMessage($method);
-    }
-
     return "The 'administer node fields' permission is required.";
   }
 
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/FieldStorageConfig/FieldStorageConfigResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/FieldStorageConfig/FieldStorageConfigResourceTestBase.php
index aafc253..817c8e8 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/FieldStorageConfig/FieldStorageConfigResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/FieldStorageConfig/FieldStorageConfigResourceTestBase.php
@@ -79,10 +79,6 @@ protected function getNormalizedPostEntity() {
    * {@inheritdoc}
    */
   protected function getExpectedUnauthorizedAccessMessage($method) {
-    if ($this->config('rest.settings')->get('bc_entity_resource_permissions')) {
-      return parent::getExpectedUnauthorizedAccessMessage($method);
-    }
-
     switch ($method) {
       case 'GET':
         return "The 'administer node fields' permission is required.";
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/ImageStyle/ImageStyleResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/ImageStyle/ImageStyleResourceTestBase.php
index ccd68d9..3dbc1ab 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/ImageStyle/ImageStyleResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/ImageStyle/ImageStyleResourceTestBase.php
@@ -103,10 +103,6 @@ protected function getNormalizedPostEntity() {
    * {@inheritdoc}
    */
   protected function getExpectedUnauthorizedAccessMessage($method) {
-    if ($this->config('rest.settings')->get('bc_entity_resource_permissions')) {
-      return parent::getExpectedUnauthorizedAccessMessage($method);
-    }
-
     return "The 'administer image styles' permission is required.";
   }
 
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/Item/ItemResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/Item/ItemResourceTestBase.php
index f217b97..8ca3005 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/Item/ItemResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/Item/ItemResourceTestBase.php
@@ -4,7 +4,6 @@
 
 use Drupal\aggregator\Entity\Feed;
 use Drupal\aggregator\Entity\Item;
-use Drupal\Tests\rest\Functional\BcTimestampNormalizerUnixTestTrait;
 use Drupal\Tests\rest\Functional\EntityResource\EntityResourceTestBase;
 
 /**
@@ -12,8 +11,6 @@
  */
 abstract class ItemResourceTestBase extends EntityResourceTestBase {
 
-  use BcTimestampNormalizerUnixTestTrait;
-
   /**
    * {@inheritdoc}
    */
@@ -116,7 +113,10 @@ protected function getExpectedNormalizedEntity() {
       'author' => [],
       'description' => [],
       'timestamp' => [
-        $this->formatExpectedTimestampItemValues(123456789),
+        [
+          'value' => (new \DateTime())->setTimestamp(123456789)->setTimezone(new \DateTimeZone('UTC'))->format(\DateTime::RFC3339),
+          'format' => \DateTime::RFC3339,
+        ],
       ],
       'guid' => [],
     ];
@@ -157,10 +157,6 @@ protected function getExpectedCacheContexts() {
    * {@inheritdoc}
    */
   protected function getExpectedUnauthorizedAccessMessage($method) {
-    if ($this->config('rest.settings')->get('bc_entity_resource_permissions')) {
-      return parent::getExpectedUnauthorizedAccessMessage($method);
-    }
-
     switch ($method) {
       case 'GET':
         return "The 'access news feeds' permission is required.";
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/MenuLinkContent/MenuLinkContentResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/MenuLinkContent/MenuLinkContentResourceTestBase.php
index 0b1f967..c01c985 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/MenuLinkContent/MenuLinkContentResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/MenuLinkContent/MenuLinkContentResourceTestBase.php
@@ -3,7 +3,6 @@
 namespace Drupal\Tests\rest\Functional\EntityResource\MenuLinkContent;
 
 use Drupal\menu_link_content\Entity\MenuLinkContent;
-use Drupal\Tests\rest\Functional\BcTimestampNormalizerUnixTestTrait;
 use Drupal\Tests\rest\Functional\EntityResource\EntityResourceTestBase;
 
 /**
@@ -11,8 +10,6 @@
  */
 abstract class MenuLinkContentResourceTestBase extends EntityResourceTestBase {
 
-  use BcTimestampNormalizerUnixTestTrait;
-
   /**
    * {@inheritdoc}
    */
@@ -164,7 +161,10 @@ protected function getExpectedNormalizedEntity() {
         ],
       ],
       'changed' => [
-        $this->formatExpectedTimestampItemValues($this->entity->getChangedTime()),
+        [
+          'value' => (new \DateTime())->setTimestamp($this->entity->getChangedTime())->setTimezone(new \DateTimeZone('UTC'))->format(\DateTime::RFC3339),
+          'format' => \DateTime::RFC3339,
+        ],
       ],
       'default_langcode' => [
         [
@@ -179,10 +179,6 @@ protected function getExpectedNormalizedEntity() {
    * {@inheritdoc}
    */
   protected function getExpectedUnauthorizedAccessMessage($method) {
-    if ($this->config('rest.settings')->get('bc_entity_resource_permissions')) {
-      return parent::getExpectedUnauthorizedAccessMessage($method);
-    }
-
     switch ($method) {
       case 'DELETE':
         return "You are not authorized to delete this menu_link_content entity.";
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/Node/NodeResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/Node/NodeResourceTestBase.php
index b4fc553..7c53063 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/Node/NodeResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/Node/NodeResourceTestBase.php
@@ -4,14 +4,11 @@
 
 use Drupal\node\Entity\Node;
 use Drupal\node\Entity\NodeType;
-use Drupal\Tests\rest\Functional\BcTimestampNormalizerUnixTestTrait;
 use Drupal\Tests\rest\Functional\EntityResource\EntityResourceTestBase;
 use Drupal\user\Entity\User;
 
 abstract class NodeResourceTestBase extends EntityResourceTestBase {
 
-  use BcTimestampNormalizerUnixTestTrait;
-
   /**
    * {@inheritdoc}
    */
@@ -128,10 +125,16 @@ protected function getExpectedNormalizedEntity() {
         ],
       ],
       'created' => [
-        $this->formatExpectedTimestampItemValues(123456789),
+        [
+          'value' => (new \DateTime())->setTimestamp(123456789)->setTimezone(new \DateTimeZone('UTC'))->format(\DateTime::RFC3339),
+          'format' => \DateTime::RFC3339,
+        ],
       ],
       'changed' => [
-        $this->formatExpectedTimestampItemValues($this->entity->getChangedTime()),
+        [
+          'value' => (new \DateTime())->setTimestamp($this->entity->getChangedTime())->setTimezone(new \DateTimeZone('UTC'))->format(\DateTime::RFC3339),
+          'format' => \DateTime::RFC3339,
+        ],
       ],
       'promote' => [
         [
@@ -144,7 +147,10 @@ protected function getExpectedNormalizedEntity() {
         ],
       ],
       'revision_timestamp' => [
-        $this->formatExpectedTimestampItemValues(123456789),
+        [
+          'value' => (new \DateTime())->setTimestamp(123456789)->setTimezone(new \DateTimeZone('UTC'))->format(\DateTime::RFC3339),
+          'format' => \DateTime::RFC3339,
+        ],
       ],
       'revision_translation_affected' => [
         [
@@ -205,10 +211,6 @@ protected function getNormalizedPostEntity() {
    * {@inheritdoc}
    */
   protected function getExpectedUnauthorizedAccessMessage($method) {
-    if ($this->config('rest.settings')->get('bc_entity_resource_permissions')) {
-      return parent::getExpectedUnauthorizedAccessMessage($method);
-    }
-
     if ($method === 'GET' || $method == 'PATCH' || $method == 'DELETE') {
       return "The 'access content' permission is required.";
     }
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/NodeType/NodeTypeResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/NodeType/NodeTypeResourceTestBase.php
index c374bfb..2bf5523 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/NodeType/NodeTypeResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/NodeType/NodeTypeResourceTestBase.php
@@ -80,10 +80,6 @@ protected function getNormalizedPostEntity() {
    * {@inheritdoc}
    */
   protected function getExpectedUnauthorizedAccessMessage($method) {
-    if ($this->config('rest.settings')->get('bc_entity_resource_permissions')) {
-      return parent::getExpectedUnauthorizedAccessMessage($method);
-    }
-
     return "The 'access content' permission is required.";
   }
 
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/SearchPage/SearchPageResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/SearchPage/SearchPageResourceTestBase.php
index e81993f..58cf9e2 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/SearchPage/SearchPageResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/SearchPage/SearchPageResourceTestBase.php
@@ -86,10 +86,6 @@ protected function getNormalizedPostEntity() {
    * {@inheritdoc}
    */
   protected function getExpectedUnauthorizedAccessMessage($method) {
-    if ($this->config('rest.settings')->get('bc_entity_resource_permissions')) {
-      return parent::getExpectedUnauthorizedAccessMessage($method);
-    }
-
     switch ($method) {
       case 'GET':
         return "The 'access content' permission is required.";
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/Shortcut/ShortcutResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/Shortcut/ShortcutResourceTestBase.php
index 36be5b5..c4cfd4b 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/Shortcut/ShortcutResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/Shortcut/ShortcutResourceTestBase.php
@@ -144,10 +144,6 @@ protected function getNormalizedPostEntity() {
    * {@inheritdoc}
    */
   protected function getExpectedUnauthorizedAccessMessage($method) {
-    if ($this->config('rest.settings')->get('bc_entity_resource_permissions')) {
-      return parent::getExpectedUnauthorizedAccessMessage($method);
-    }
-
     switch ($method) {
       case 'GET':
       case 'POST':
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/Term/TermResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/Term/TermResourceTestBase.php
index 44a4e83..2bec08a 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/Term/TermResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/Term/TermResourceTestBase.php
@@ -4,13 +4,10 @@
 
 use Drupal\taxonomy\Entity\Term;
 use Drupal\taxonomy\Entity\Vocabulary;
-use Drupal\Tests\rest\Functional\BcTimestampNormalizerUnixTestTrait;
 use Drupal\Tests\rest\Functional\EntityResource\EntityResourceTestBase;
 
 abstract class TermResourceTestBase extends EntityResourceTestBase {
 
-  use BcTimestampNormalizerUnixTestTrait;
-
   /**
    * {@inheritdoc}
    */
@@ -115,7 +112,10 @@ protected function getExpectedNormalizedEntity() {
         ],
       ],
       'changed' => [
-        $this->formatExpectedTimestampItemValues($this->entity->getChangedTime()),
+        [
+          'value' => (new \DateTime())->setTimestamp($this->entity->getChangedTime())->setTimezone(new \DateTimeZone('UTC'))->format(\DateTime::RFC3339),
+          'format' => \DateTime::RFC3339,
+        ],
       ],
       'default_langcode' => [
         [
@@ -160,10 +160,6 @@ protected function getNormalizedPostEntity() {
    * {@inheritdoc}
    */
   protected function getExpectedUnauthorizedAccessMessage($method) {
-    if ($this->config('rest.settings')->get('bc_entity_resource_permissions')) {
-      return parent::getExpectedUnauthorizedAccessMessage($method);
-    }
-
     switch ($method) {
       case 'GET':
         return "The 'access content' permission is required.";
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/Tour/TourResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/Tour/TourResourceTestBase.php
index 294e3ee..7f0b99a 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/Tour/TourResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/Tour/TourResourceTestBase.php
@@ -113,10 +113,6 @@ protected function getExpectedCacheContexts() {
    * {@inheritdoc}
    */
   protected function getExpectedUnauthorizedAccessMessage($method) {
-    if ($this->config('rest.settings')->get('bc_entity_resource_permissions')) {
-      return parent::getExpectedUnauthorizedAccessMessage($method);
-    }
-
     return "The following permissions are required: 'access tour' OR 'administer site configuration'.";
   }
 
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/User/UserResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/User/UserResourceTestBase.php
index caf2909..625d1f7 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/User/UserResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/User/UserResourceTestBase.php
@@ -3,15 +3,12 @@
 namespace Drupal\Tests\rest\Functional\EntityResource\User;
 
 use Drupal\Core\Url;
-use Drupal\Tests\rest\Functional\BcTimestampNormalizerUnixTestTrait;
 use Drupal\Tests\rest\Functional\EntityResource\EntityResourceTestBase;
 use Drupal\user\Entity\User;
 use GuzzleHttp\RequestOptions;
 
 abstract class UserResourceTestBase extends EntityResourceTestBase {
 
-  use BcTimestampNormalizerUnixTestTrait;
-
   /**
    * {@inheritdoc}
    */
@@ -101,10 +98,16 @@ protected function getExpectedNormalizedEntity() {
         ],
       ],
       'created' => [
-        $this->formatExpectedTimestampItemValues(123456789),
+        [
+          'value' => (new \DateTime())->setTimestamp(123456789)->setTimezone(new \DateTimeZone('UTC'))->format(\DateTime::RFC3339),
+          'format' => \DateTime::RFC3339,
+        ],
       ],
       'changed' => [
-        $this->formatExpectedTimestampItemValues($this->entity->getChangedTime()),
+        [
+          'value' => (new \DateTime())->setTimestamp($this->entity->getChangedTime())->setTimezone(new \DateTimeZone('UTC'))->format(\DateTime::RFC3339),
+          'format' => \DateTime::RFC3339,
+        ],
       ],
       'default_langcode' => [
         [
@@ -263,10 +266,6 @@ protected function assertRpcLogin($username, $password) {
    * {@inheritdoc}
    */
   protected function getExpectedUnauthorizedAccessMessage($method) {
-    if ($this->config('rest.settings')->get('bc_entity_resource_permissions')) {
-      return parent::getExpectedUnauthorizedAccessMessage($method);
-    }
-
     switch ($method) {
       case 'GET':
         return "The 'access user profiles' permission is required and the user must be active.";
diff --git a/core/modules/rest/tests/src/Functional/Update/EntityResourcePermissionsUpdateTest.php b/core/modules/rest/tests/src/Functional/Update/EntityResourcePermissionsUpdateTest.php
deleted file mode 100644
index 9add9c5..0000000
--- a/core/modules/rest/tests/src/Functional/Update/EntityResourcePermissionsUpdateTest.php
+++ /dev/null
@@ -1,56 +0,0 @@
-<?php
-
-namespace Drupal\Tests\rest\Functional\Update;
-
-use Drupal\FunctionalTests\Update\UpdatePathTestBase;
-
-/**
- * Tests that existing sites continue to use permissions for EntityResource.
- *
- * @see https://www.drupal.org/node/2664780
- *
- * @group rest
- */
-class EntityResourcePermissionsUpdateTest extends UpdatePathTestBase {
-
-  /**
-   * {@inheritdoc}
-   */
-  protected static $modules = ['rest', 'serialization'];
-
-  /**
-   * {@inheritdoc}
-   */
-  public function setDatabaseDumpFiles() {
-    $this->databaseDumpFiles = [
-      __DIR__ . '/../../../../../system/tests/fixtures/update/drupal-8.bare.standard.php.gz',
-      __DIR__ . '/../../../fixtures/update/drupal-8.rest-rest_update_8203.php',
-    ];
-  }
-
-  /**
-   * Tests rest_update_8203().
-   */
-  public function testBcEntityResourcePermissionSettingAdded() {
-    $permission_handler = $this->container->get('user.permissions');
-
-    $is_rest_resource_permission = function ($permission) {
-      return $permission['provider'] === 'rest' && (string) $permission['title'] !== 'Administer REST resource configuration';
-    };
-
-    // Make sure we have the expected values before the update.
-    $rest_settings = $this->config('rest.settings');
-    $this->assertFalse(array_key_exists('bc_entity_resource_permissions', $rest_settings->getRawData()));
-    $this->assertEqual([], array_filter($permission_handler->getPermissions(), $is_rest_resource_permission));
-
-    $this->runUpdates();
-
-    // Make sure we have the expected values after the update.
-    $rest_settings = $this->config('rest.settings');
-    $this->assertTrue(array_key_exists('bc_entity_resource_permissions', $rest_settings->getRawData()));
-    $this->assertTrue($rest_settings->get('bc_entity_resource_permissions'));
-    $rest_permissions = array_keys(array_filter($permission_handler->getPermissions(), $is_rest_resource_permission));
-    $this->assertEqual(['restful delete entity:node', 'restful get entity:node', 'restful patch entity:node', 'restful post entity:node'], $rest_permissions);
-  }
-
-}
diff --git a/core/modules/rest/tests/src/Functional/Update/ResourceGranularityUpdateTest.php b/core/modules/rest/tests/src/Functional/Update/ResourceGranularityUpdateTest.php
deleted file mode 100644
index 19ef545..0000000
--- a/core/modules/rest/tests/src/Functional/Update/ResourceGranularityUpdateTest.php
+++ /dev/null
@@ -1,71 +0,0 @@
-<?php
-
-namespace Drupal\Tests\rest\Functional\Update;
-
-use Drupal\FunctionalTests\Update\UpdatePathTestBase;
-
-/**
- * Tests method-granularity REST config is simplified to resource-granularity.
- *
- * @see https://www.drupal.org/node/2721595
- * @see rest_post_update_resource_granularity()
- *
- * @group rest
- */
-class ResourceGranularityUpdateTest extends UpdatePathTestBase {
-
-  /**
-   * {@inheritdoc}
-   */
-  protected static $modules = ['rest', 'serialization'];
-
-  /**
-   * {@inheritdoc}
-   */
-  public function setDatabaseDumpFiles() {
-    $this->databaseDumpFiles = [
-      __DIR__ . '/../../../../../system/tests/fixtures/update/drupal-8.bare.standard.php.gz',
-      __DIR__ . '/../../../fixtures/update/drupal-8.rest-rest_post_update_resource_granularity.php',
-    ];
-  }
-
-  /**
-   * Tests rest_post_update_simplify_resource_granularity().
-   */
-  public function testMethodGranularityConvertedToResourceGranularity() {
-    /** @var \Drupal\Core\Entity\EntityStorageInterface $resource_config_storage */
-    $resource_config_storage = $this->container->get('entity_type.manager')->getStorage('rest_resource_config');
-
-    // Make sure we have the expected values before the update.
-    $resource_config_entities = $resource_config_storage->loadMultiple();
-    $this->assertIdentical(['entity.comment', 'entity.node', 'entity.user'], array_keys($resource_config_entities));
-    $this->assertIdentical('method', $resource_config_entities['entity.node']->get('granularity'));
-    $this->assertIdentical('method', $resource_config_entities['entity.comment']->get('granularity'));
-    $this->assertIdentical('method', $resource_config_entities['entity.user']->get('granularity'));
-
-    // Read the existing 'entity:comment' and 'entity:user' resource
-    // configuration so we can verify it after the update.
-    $comment_resource_configuration = $resource_config_entities['entity.comment']->get('configuration');
-    $user_resource_configuration = $resource_config_entities['entity.user']->get('configuration');
-
-    $this->runUpdates();
-
-    // Make sure we have the expected values after the update.
-    $resource_config_entities = $resource_config_storage->loadMultiple();
-    $this->assertIdentical(['entity.comment', 'entity.node', 'entity.user'], array_keys($resource_config_entities));
-    // 'entity:node' should be updated.
-    $this->assertIdentical('resource', $resource_config_entities['entity.node']->get('granularity'));
-    $this->assertidentical($resource_config_entities['entity.node']->get('configuration'), [
-      'methods' => ['GET', 'POST', 'PATCH', 'DELETE'],
-      'formats' => ['hal_json'],
-      'authentication' => ['basic_auth'],
-    ]);
-    // 'entity:comment' should be unchanged.
-    $this->assertIdentical('method', $resource_config_entities['entity.comment']->get('granularity'));
-    $this->assertIdentical($comment_resource_configuration, $resource_config_entities['entity.comment']->get('configuration'));
-    // 'entity:user' should be unchanged.
-    $this->assertIdentical('method', $resource_config_entities['entity.user']->get('granularity'));
-    $this->assertIdentical($user_resource_configuration, $resource_config_entities['entity.user']->get('configuration'));
-  }
-
-}
diff --git a/core/modules/rest/tests/src/Functional/Update/RestConfigurationEntitiesUpdateTest.php b/core/modules/rest/tests/src/Functional/Update/RestConfigurationEntitiesUpdateTest.php
deleted file mode 100644
index f4d8199..0000000
--- a/core/modules/rest/tests/src/Functional/Update/RestConfigurationEntitiesUpdateTest.php
+++ /dev/null
@@ -1,65 +0,0 @@
-<?php
-
-namespace Drupal\Tests\rest\Functional\Update;
-
-use Drupal\FunctionalTests\Update\UpdatePathTestBase;
-use Drupal\rest\RestResourceConfigInterface;
-
-/**
- * Tests that rest.settings is converted to rest_resource_config entities.
- *
- * @see https://www.drupal.org/node/2308745
- * @see rest_update_8201()
- * @see rest_post_update_create_rest_resource_config_entities()
- *
- * @group rest
- */
-class RestConfigurationEntitiesUpdateTest extends UpdatePathTestBase {
-
-  /**
-   * {@inheritdoc}
-   */
-  protected static $modules = ['rest', 'serialization'];
-
-  /**
-   * {@inheritdoc}
-   */
-  public function setDatabaseDumpFiles() {
-    $this->databaseDumpFiles = [
-      __DIR__ . '/../../../../../system/tests/fixtures/update/drupal-8.bare.standard.php.gz',
-      __DIR__ . '/../../../fixtures/update/drupal-8.rest-rest_update_8201.php',
-    ];
-  }
-
-  /**
-   * Tests rest_update_8201().
-   */
-  public function testResourcesConvertedToConfigEntities() {
-    /** @var \Drupal\Core\Entity\EntityStorageInterface $resource_config_storage */
-    $resource_config_storage = $this->container->get('entity_type.manager')->getStorage('rest_resource_config');
-
-    // Make sure we have the expected values before the update.
-    $rest_settings = $this->config('rest.settings');
-    $this->assertTrue(array_key_exists('resources', $rest_settings->getRawData()));
-    $this->assertTrue(array_key_exists('entity:node', $rest_settings->getRawData()['resources']));
-    $resource_config_entities = $resource_config_storage->loadMultiple();
-    $this->assertIdentical([], array_keys($resource_config_entities));
-
-    $this->runUpdates();
-
-    // Make sure we have the expected values after the update.
-    $rest_settings = $this->config('rest.settings');
-    $this->assertFalse(array_key_exists('resources', $rest_settings->getRawData()));
-    $resource_config_entities = $resource_config_storage->loadMultiple();
-    $this->assertIdentical(['entity.node'], array_keys($resource_config_entities));
-    $node_resource_config_entity = $resource_config_entities['entity.node'];
-    $this->assertIdentical(RestResourceConfigInterface::RESOURCE_GRANULARITY, $node_resource_config_entity->get('granularity'));
-    $this->assertIdentical([
-      'methods' => ['GET'],
-      'formats' => ['json'],
-      'authentication' => ['basic_auth'],
-    ], $node_resource_config_entity->get('configuration'));
-    $this->assertIdentical(['module' => ['basic_auth', 'node', 'serialization']], $node_resource_config_entity->getDependencies());
-  }
-
-}
diff --git a/core/modules/rest/tests/src/Functional/Update/RestExportAuthUpdateTest.php b/core/modules/rest/tests/src/Functional/Update/RestExportAuthUpdateTest.php
deleted file mode 100644
index 87cd5db..0000000
--- a/core/modules/rest/tests/src/Functional/Update/RestExportAuthUpdateTest.php
+++ /dev/null
@@ -1,36 +0,0 @@
-<?php
-
-namespace Drupal\Tests\rest\Functional\Update;
-
-use Drupal\FunctionalTests\Update\UpdatePathTestBase;
-
-/**
- * Ensures that update hook is run properly for REST Export config.
- *
- * @group Update
- */
-class RestExportAuthUpdateTest extends UpdatePathTestBase {
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function setDatabaseDumpFiles() {
-    $this->databaseDumpFiles = [
-      __DIR__ . '/../../../../../system/tests/fixtures/update/drupal-8.bare.standard.php.gz',
-      __DIR__ . '/../../../../tests/fixtures/update/rest-export-with-authentication.php',
-    ];
-  }
-
-  /**
-   * Ensures that update hook is run for rest module.
-   */
-  public function testUpdate() {
-    $this->runUpdates();
-
-    // Get particular view.
-    $view = \Drupal::entityTypeManager()->getStorage('view')->load('rest_export_with_authorization');
-    $displays = $view->get('display');
-    $this->assertIdentical($displays['rest_export_1']['display_options']['auth']['basic_auth'], 'basic_auth', 'Basic authentication is set as authentication method.');
-  }
-
-}