.../MenuLinkContent/MenuLinkContentXmlAnonTest.php | 26 ++++++++++++++++
 .../MenuLinkContentXmlBasicAuthTest.php            | 36 ++++++++++++++++++++++
 .../MenuLinkContentXmlCookieTest.php               | 31 +++++++++++++++++++
 .../src/Functional/XmlNormalizationQuirksTrait.php |  5 ++-
 4 files changed, 97 insertions(+), 1 deletion(-)

diff --git a/core/modules/rest/tests/src/Functional/EntityResource/MenuLinkContent/MenuLinkContentXmlAnonTest.php b/core/modules/rest/tests/src/Functional/EntityResource/MenuLinkContent/MenuLinkContentXmlAnonTest.php
new file mode 100644
index 0000000..5141cb7
--- /dev/null
+++ b/core/modules/rest/tests/src/Functional/EntityResource/MenuLinkContent/MenuLinkContentXmlAnonTest.php
@@ -0,0 +1,26 @@
+<?php
+
+namespace Drupal\Tests\rest\Functional\EntityResource\MenuLinkContent;
+
+use Drupal\Tests\rest\Functional\AnonResourceTestTrait;
+use Drupal\Tests\rest\Functional\EntityResource\XmlEntityNormalizationQuirksTrait;
+
+/**
+ * @group rest
+ */
+class MenuLinkContentXmlAnonTest extends MenuLinkContentResourceTestBase {
+
+  use AnonResourceTestTrait;
+  use XmlEntityNormalizationQuirksTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $format = 'xml';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $mimeType = 'text/xml; charset=UTF-8';
+
+}
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/MenuLinkContent/MenuLinkContentXmlBasicAuthTest.php b/core/modules/rest/tests/src/Functional/EntityResource/MenuLinkContent/MenuLinkContentXmlBasicAuthTest.php
new file mode 100644
index 0000000..6a62f36
--- /dev/null
+++ b/core/modules/rest/tests/src/Functional/EntityResource/MenuLinkContent/MenuLinkContentXmlBasicAuthTest.php
@@ -0,0 +1,36 @@
+<?php
+
+namespace Drupal\Tests\rest\Functional\EntityResource\MenuLinkContent;
+
+use Drupal\Tests\rest\Functional\BasicAuthResourceTestTrait;
+use Drupal\Tests\rest\Functional\EntityResource\XmlEntityNormalizationQuirksTrait;
+
+/**
+ * @group rest
+ */
+class MenuLinkContentXmlBasicAuthTest extends MenuLinkContentResourceTestBase {
+
+  use BasicAuthResourceTestTrait;
+  use XmlEntityNormalizationQuirksTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = ['basic_auth'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $format = 'xml';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $mimeType = 'text/xml; charset=UTF-8';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $auth = 'basic_auth';
+
+}
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/MenuLinkContent/MenuLinkContentXmlCookieTest.php b/core/modules/rest/tests/src/Functional/EntityResource/MenuLinkContent/MenuLinkContentXmlCookieTest.php
new file mode 100644
index 0000000..f73d493
--- /dev/null
+++ b/core/modules/rest/tests/src/Functional/EntityResource/MenuLinkContent/MenuLinkContentXmlCookieTest.php
@@ -0,0 +1,31 @@
+<?php
+
+namespace Drupal\Tests\rest\Functional\EntityResource\MenuLinkContent;
+
+use Drupal\Tests\rest\Functional\CookieResourceTestTrait;
+use Drupal\Tests\rest\Functional\EntityResource\XmlEntityNormalizationQuirksTrait;
+
+/**
+ * @group rest
+ */
+class MenuLinkContentXmlCookieTest extends MenuLinkContentResourceTestBase {
+
+  use CookieResourceTestTrait;
+  use XmlEntityNormalizationQuirksTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $format = 'xml';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $mimeType = 'text/xml; charset=UTF-8';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $auth = 'cookie';
+
+}
diff --git a/core/modules/rest/tests/src/Functional/XmlNormalizationQuirksTrait.php b/core/modules/rest/tests/src/Functional/XmlNormalizationQuirksTrait.php
index 11c77810..4c7c455 100644
--- a/core/modules/rest/tests/src/Functional/XmlNormalizationQuirksTrait.php
+++ b/core/modules/rest/tests/src/Functional/XmlNormalizationQuirksTrait.php
@@ -23,9 +23,12 @@
    */
   protected function applyXmlDecodingQuirks(array $normalization) {
     foreach ($normalization as $key => $value) {
-      if ($value === []) {
+      if ($value === [] || $value === NULL) {
         $normalization[$key] = '';
       }
+      elseif (is_array($value)) {
+        $normalization[$key] = $this->applyXmlDecodingQuirks($value);
+      }
     }
     return $normalization;
   }