diff --git a/core/modules/system/src/Tests/ComposerWebTest.php b/core/modules/system/src/Tests/ComposerWebTest.php
index 261989b..2b74b6d 100644
--- a/core/modules/system/src/Tests/ComposerWebTest.php
+++ b/core/modules/system/src/Tests/ComposerWebTest.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Contains \Drupal\action\Tests\ActionUninstallTest.
+ * Contains \Drupal\system\Tests\ComposerWebTest.
  */
 
 namespace Drupal\system\Tests;
@@ -24,7 +24,8 @@ class ComposerWebTest extends WebTestBase {
   public static $modules = [];
 
   /**
-   * Test to see if all modules are in the replace array of core's composer.json
+   * Verify all modules are listed in the 'replace' section of core's
+   * composer.json.
    */
   public function testAllModulesReplaced() {
     $root = dirname(dirname(substr(__DIR__, 0, -strlen(__NAMESPACE__))));
@@ -32,12 +33,12 @@ public function testAllModulesReplaced() {
     $json = json_decode(file_get_contents($root . '/core/composer.json'));
     $composer_replace_packages = $json->replace;
 
-    $modules = system_rebuild_module_data();
+    $folders = scandir($root . '/core/modules');
     $module_names = [];
 
-    foreach ($modules as $name => $module) {
-      if (strpos($module->getPathname(), '/tests/') === false && strpos($module->getPathname(), '/profiles/testing/') === false) {
-        $module_names[] = $name;
+    foreach ($folders as $file_name) {
+      if ($file_name !== '.' && $file_name !== '..') {
+        $module_names[] = $file_name;
       }
     }