diff --git a/core/.phpstan-baseline.php b/core/.phpstan-baseline.php
index a7029995ffe0f0cff3537756c1bfad2091111a57..062692890548aa51b17f7336800aff524e1eb9da 100644
--- a/core/.phpstan-baseline.php
+++ b/core/.phpstan-baseline.php
@@ -1614,12 +1614,6 @@
 	'count' => 1,
 	'path' => __DIR__ . '/modules/serialization/src/Normalizer/EntityNormalizer.php',
 ];
-$ignoreErrors[] = [
-	// identifier: method.deprecated
-	'message' => '#^Call to deprecated method getMockForAbstractClass\\(\\) of class PHPUnit\\\\Framework\\\\TestCase\\.$#',
-	'count' => 1,
-	'path' => __DIR__ . '/modules/serialization/tests/src/Unit/Normalizer/NormalizerBaseTest.php',
-];
 $ignoreErrors[] = [
 	// identifier: return.missing
 	'message' => '#^Method Drupal\\\\shortcut\\\\Form\\\\SetCustomize\\:\\:save\\(\\) should return int but return statement is missing\\.$#',
diff --git a/core/modules/serialization/tests/src/Unit/Normalizer/NormalizerBaseTest.php b/core/modules/serialization/tests/src/Unit/Normalizer/NormalizerBaseTest.php
index 8fe665113e2208e1a569bc523745af8ab05e3237..743a2d7b192e1efda8680d534722944ff3db0030 100644
--- a/core/modules/serialization/tests/src/Unit/Normalizer/NormalizerBaseTest.php
+++ b/core/modules/serialization/tests/src/Unit/Normalizer/NormalizerBaseTest.php
@@ -26,7 +26,7 @@ class NormalizerBaseTest extends UnitTestCase {
    *   (optional) The supported interface or class to set on the normalizer.
    */
   public function testSupportsNormalization($expected_return, $data, $supported_types = NULL): void {
-    $normalizer_base = $this->getMockForAbstractClass('Drupal\Tests\serialization\Unit\Normalizer\TestNormalizerBase');
+    $normalizer_base = new TestNormalizerBase();
 
     if (isset($supported_types)) {
       $normalizer_base->setSupportedTypes($supported_types);
@@ -61,9 +61,9 @@ public static function providerTestSupportsNormalization() {
 }
 
 /**
- * Test class for NormalizerBase.
+ * Testable class for NormalizerBase.
  */
-abstract class TestNormalizerBase extends NormalizerBase {
+class TestNormalizerBase extends NormalizerBase {
 
   /**
    * The interface or class that this Normalizer supports.
@@ -89,4 +89,11 @@ public function getSupportedTypes(?string $format): array {
     return $this->supportedTypes;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function normalize($object, $format = NULL, array $context = []): array|string|int|float|bool|\ArrayObject|NULL {
+    return NULL;
+  }
+
 }