diff --git a/core/modules/file/tests/src/Traits/FileFieldTestBaseTrait.php b/core/modules/file/tests/src/Traits/FileFieldTestBaseTrait.php
index 897101e84b..9ce7058603 100644
--- a/core/modules/file/tests/src/Traits/FileFieldTestBaseTrait.php
+++ b/core/modules/file/tests/src/Traits/FileFieldTestBaseTrait.php
@@ -7,8 +7,6 @@
 use Drupal\file\FileInterface;
 use Drupal\file\Entity\File;
 use Drupal\Tests\TestFileCreationTrait;
-use Drupal\Tests\Traits\DrupalPostFormHack;
-use Drupal\Tests\Traits\DrupalPostFormWithInvalidOptionsTrait;
 use Drupal\user\UserInterface;
 
 /**
diff --git a/core/tests/Drupal/Tests/Traits/DrupalPostFormWithInvalidOptionsTrait.php b/core/tests/Drupal/Tests/Traits/DrupalPostFormWithInvalidOptionsTrait.php
index c9ffa40bb6..54363caad1 100644
--- a/core/tests/Drupal/Tests/Traits/DrupalPostFormWithInvalidOptionsTrait.php
+++ b/core/tests/Drupal/Tests/Traits/DrupalPostFormWithInvalidOptionsTrait.php
@@ -96,13 +96,24 @@ protected function drupalPostFormWithInvalidOptions($path = NULL, array $edit =
     $edit_params = $this->getPhpValues($edit_params);
     $edit_multipart = $this->getPhpValues($edit_multipart);
 
+    if (isset($form_multipart['files']) && isset($edit_multipart['files'])) {
+      foreach ($form_multipart['files'] as $key => $file) {
+        if (isset($edit_multipart['files'][$key])) {
+          foreach ($edit_multipart['files'][$key] as $edit_file) {
+            $form_multipart['files'][$key][] = $edit_file;
+          }
+          unset($edit_multipart['files'][$key]);
+        }
+      }
+    }
+
     // Get raw edit values.
     $raw_edit_params = isset($raw_edit['form_params']) ? $raw_edit['form_params'] : [];
     $raw_edit_multipart = isset($raw_edit['multipart']) ? $raw_edit['multipart'] : [];
 
     // Combine form, edit and raw values.
-    $params = array_merge($form_params, $edit_params, $raw_edit_params);
-    $multipart = array_merge($form_multipart, $edit_multipart, $raw_edit_multipart);
+    $params = array_replace_recursive($form_params, $edit_params, $raw_edit_params);
+    $multipart = array_replace_recursive($form_multipart, $edit_multipart, $raw_edit_multipart);
 
     $this->prepareRequest();