.../tests/src/Functional/EntityResource/EntityResourceTestBase.php    | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
index d1a5ac0..2542912 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
@@ -19,6 +19,7 @@
 use Drupal\path\Plugin\Field\FieldType\PathItem;
 use Drupal\rest\ResourceResponseInterface;
 use Drupal\Tests\rest\Functional\ResourceTestBase;
+use Drupal\Tests\Traits\ExpectDeprecationTrait;
 use GuzzleHttp\RequestOptions;
 use Psr\Http\Message\ResponseInterface;
 use Symfony\Component\Routing\Exception\RouteNotFoundException;
@@ -73,6 +74,8 @@
  */
 abstract class EntityResourceTestBase extends ResourceTestBase {
 
+  use ExpectDeprecationTrait;
+
   /**
    * The tested entity type.
    *
@@ -708,6 +711,7 @@ public function testGet() {
     // new and old sites, but trigger deprecation notices.
     $bc_route = Url::fromRoute('rest.entity.' . static::$entityTypeId . '.GET.' . static::$format, $url->getRouteParameters(), $url->getOptions());
     $bc_route->setUrlGenerator($this->container->get('url_generator'));
+    $this->expectDeprecation(sprintf("The 'rest.entity.%s.GET.%s' route is deprecated since version 8.5.x and will be removed in 9.0.0. Use the 'rest.entity.%s.%s' route instead.", static::$entityTypeId, static::$format, static::$entityTypeId, static::$format));
     $this->assertSame($url->toString(TRUE)->getGeneratedUrl(), $bc_route->toString(TRUE)->getGeneratedUrl());
     // Verify no format-specific GET BC routes are created for other formats.
     $other_format = static::$format === 'json' ? 'xml' : 'json';