.../EntityResource/Feed/FeedXmlAnonTest.php        | 26 ++++++++++++++
 .../EntityResource/Feed/FeedXmlBasicAuthTest.php   | 40 ++++++++++++++++++++++
 .../EntityResource/Feed/FeedXmlCookieTest.php      | 31 +++++++++++++++++
 .../XmlEntityNormalizationQuirksTrait.php          |  4 +++
 4 files changed, 101 insertions(+)

diff --git a/core/modules/rest/tests/src/Functional/EntityResource/Feed/FeedXmlAnonTest.php b/core/modules/rest/tests/src/Functional/EntityResource/Feed/FeedXmlAnonTest.php
new file mode 100644
index 0000000..f2a3233
--- /dev/null
+++ b/core/modules/rest/tests/src/Functional/EntityResource/Feed/FeedXmlAnonTest.php
@@ -0,0 +1,26 @@
+<?php
+
+namespace Drupal\Tests\rest\Functional\EntityResource\Feed;
+
+use Drupal\Tests\rest\Functional\AnonResourceTestTrait;
+use Drupal\Tests\rest\Functional\EntityResource\XmlEntityNormalizationQuirksTrait;
+
+/**
+ * @group rest
+ */
+class FeedXmlAnonTest extends FeedResourceTestBase {
+
+  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/Feed/FeedXmlBasicAuthTest.php b/core/modules/rest/tests/src/Functional/EntityResource/Feed/FeedXmlBasicAuthTest.php
new file mode 100644
index 0000000..3a8b69e
--- /dev/null
+++ b/core/modules/rest/tests/src/Functional/EntityResource/Feed/FeedXmlBasicAuthTest.php
@@ -0,0 +1,40 @@
+<?php
+
+namespace Drupal\Tests\rest\Functional\EntityResource\Feed;
+
+use Drupal\Tests\rest\Functional\BasicAuthResourceTestTrait;
+use Drupal\Tests\rest\Functional\EntityResource\XmlEntityNormalizationQuirksTrait;
+
+/**
+ * @group rest
+ */
+class FeedXmlBasicAuthTest extends FeedResourceTestBase {
+
+  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';
+
+  public function testGet() {
+    return parent::testGet(); // TODO: Change the autogenerated stub
+  }
+
+}
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/Feed/FeedXmlCookieTest.php b/core/modules/rest/tests/src/Functional/EntityResource/Feed/FeedXmlCookieTest.php
new file mode 100644
index 0000000..377690a
--- /dev/null
+++ b/core/modules/rest/tests/src/Functional/EntityResource/Feed/FeedXmlCookieTest.php
@@ -0,0 +1,31 @@
+<?php
+
+namespace Drupal\Tests\rest\Functional\EntityResource\Feed;
+
+use Drupal\Tests\rest\Functional\CookieResourceTestTrait;
+use Drupal\Tests\rest\Functional\EntityResource\XmlEntityNormalizationQuirksTrait;
+
+/**
+ * @group rest
+ */
+class FeedXmlCookieTest extends FeedResourceTestBase {
+
+  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/EntityResource/XmlEntityNormalizationQuirksTrait.php b/core/modules/rest/tests/src/Functional/EntityResource/XmlEntityNormalizationQuirksTrait.php
index bed4f26..e05ef66 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/XmlEntityNormalizationQuirksTrait.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/XmlEntityNormalizationQuirksTrait.php
@@ -8,6 +8,8 @@
 use Drupal\Core\Field\Plugin\Field\FieldType\CreatedItem;
 use Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem;
 use Drupal\Core\Field\Plugin\Field\FieldType\IntegerItem;
+use Drupal\Core\Field\Plugin\Field\FieldType\TimestampItem;
+use Drupal\options\Plugin\Field\FieldType\ListIntegerItem;
 use Drupal\path\Plugin\Field\FieldType\PathItem;
 use Drupal\Tests\rest\Functional\XmlNormalizationQuirksTrait;
 
@@ -62,6 +64,7 @@ protected function applyXmlFieldDecodingQuirks(array $normalization) {
             $value = $value === TRUE ? '1' : '0';
             break;
           case IntegerItem::class:
+          case ListIntegerItem::class:
             $value = &$normalization[$field_name][$i]['value'];
             $value = (string) $value;
             break;
@@ -75,6 +78,7 @@ protected function applyXmlFieldDecodingQuirks(array $normalization) {
             break;
           case ChangedItem::class:
           case CreatedItem::class:
+          case TimestampItem::class:
             $value = &$normalization[$field_name][$i]['value'];
             if (is_numeric($value)) {
               $value = (string) $value;