diff --git a/core/tests/Drupal/Tests/Component/PhpStorage/FileStorageTest.php b/core/tests/Drupal/Tests/Component/PhpStorage/FileStorageTest.php
index 17042c2..5944e5d 100644
--- a/core/tests/Drupal/Tests/Component/PhpStorage/FileStorageTest.php
+++ b/core/tests/Drupal/Tests/Component/PhpStorage/FileStorageTest.php
@@ -94,7 +94,22 @@ public function testDeleteAll() {
     // Make sure directory exists prior to removal.
     $this->assertTrue(file_exists(sys_get_temp_dir() . '/php/simpletest'), 'File storage directory does not exist.');
 
+    // Write out some files.
     $php = $this->storageFactory->get('simpletest');
+    $name = $this->randomName() . '/' . $this->randomName() . '.php';
+
+    // Find a global that doesn't exist.
+    do {
+      $random = mt_rand(10000, 100000);
+    } while (isset($GLOBALS[$random]));
+
+    // Write out a PHP file and ensure it's successfully loaded.
+    $code = "<?php\n\$GLOBALS[$random] = TRUE;";
+    $success = $php->save($name, $code);
+    $this->assertSame($success, TRUE);
+    $php->load($name);
+    $this->assertTrue($GLOBALS[$random]);
+
     $this->assertTrue($php->deleteAll());
     $this->assertFalse(file_exists(sys_get_temp_dir() . '/php/simpletest'), 'File storage directory still exists after call to deleteAll().');