diff -u b/core/modules/editor/src/Tests/EditorPrivateFileReferenceFilterTest.php b/core/modules/editor/src/Tests/EditorPrivateFileReferenceFilterTest.php
--- b/core/modules/editor/src/Tests/EditorPrivateFileReferenceFilterTest.php
+++ b/core/modules/editor/src/Tests/EditorPrivateFileReferenceFilterTest.php
@@ -4,14 +4,14 @@
 
 use Drupal\file\Entity\File;
 use Drupal\file\FileInterface;
-use Drupal\simpletest\WebTestBase;
+use Drupal\Tests\BrowserTestBase;
 
 /**
  * Tests Editor module's file reference filter with private files.
  *
  * @group editor
  */
-class EditorPrivateFileReferenceFilterTest extends WebTestBase {
+class EditorPrivateFileReferenceFilterTest extends BrowserTestBase {
 
   /**
    * Modules to enable.
@@ -36,6 +36,9 @@
    * Tests the editor file reference filter with private files.
    */
   function testEditorPrivateFileReferenceFilter() {
+    $author = $this->drupalCreateUser();
+    $this->drupalLogin($author);
+
     // Create a content type with a body field.
     $this->drupalCreateContentType(['type' => 'page', 'name' => 'Basic page']);
 
@@ -45,12 +48,25 @@
     /** @var FileInterface $file */
     $file = File::create([
       'uri' => 'private://' . $filename,
-      'status' => FILE_STATUS_PERMANENT,
     ]);
+    $file->setTemporary();
+    $file->setOwner($author);
     // Create the file itself.
     file_put_contents($file->getFileUri(), $this->randomString());
     $file->save();
 
+    // The image should be visible for its author.
+    $this->drupalGet($src);
+    $this->assertSession()->statusCodeEquals(200);
+    // The not-yet-permanent image should NOT be visible for anonymous.
+    $this->drupalLogout();
+    $this->drupalGet($src);
+    $this->assertSession()->statusCodeEquals(403);
+
+    // Resave the file to be permanent.
+    $file->setPermanent();
+    $file->save();
+
     // Create a node with its body field properly pointing to the just-created
     // file.
     $node = $this->drupalCreateNode([
@@ -59,12 +75,13 @@
         'value' => '<img alt="alt" data-entity-type="file" data-entity-uuid="' . $file->uuid() . '" src="' . $src . '" />',
         'format' => 'private_images',
       ],
+      'uid' => $author->id(),
     ]);
     $this->drupalGet('/node/' . $node->id());
 
     // Do the actual test. The image should be visible for anonymous.
     $this->drupalGet($src);
-    $this->assertResponse(200, 'Image is downloadable as anonymous.');
+    $this->assertSession()->statusCodeEquals(200);
   }
 
 }