diff --git a/core/modules/file/src/Tests/ValidatorTest.php b/core/modules/file/src/Tests/ValidatorTest.php
index d7f3af3..54c7173 100644
--- a/core/modules/file/src/Tests/ValidatorTest.php
+++ b/core/modules/file/src/Tests/ValidatorTest.php
@@ -45,6 +45,15 @@ function testFileValidateExtensions() {
   }
 
   /**
+   * Test the file_munge_filename() function.
+   */
+  function testFileMungeFilename() {
+    $this->assertNotEqual('file.foo.txt', file_munge_filename('file.foo.txt', 'asdf txt pork', FALSE), 'Altered invalid extra extension.', 'File');
+    $this->assertEqual('file.asdf.txt', file_munge_filename('file.asdf.txt', 'asdf txt pork', FALSE), 'Accepted valid same case extra extension.', 'File');
+    $this->assertEqual('file.Asdf.txt', file_munge_filename('file.Asdf.txt', 'asdf txt pork', FALSE), 'Accepted valid different case extra extension.', 'File');
+  }
+
+  /**
    *  This ensures a specific file is actually an image.
    */
   function testFileValidateIsImage() {