diff --git a/core/modules/system/src/Tests/Asset/ResolvedLibraryDefinitionsFilesMatchTest.php b/core/modules/system/src/Tests/Asset/ResolvedLibraryDefinitionsFilesMatchTest.php
index 4aeadd3..f894d1d 100644
--- a/core/modules/system/src/Tests/Asset/ResolvedLibraryDefinitionsFilesMatchTest.php
+++ b/core/modules/system/src/Tests/Asset/ResolvedLibraryDefinitionsFilesMatchTest.php
@@ -72,6 +72,16 @@ class ResolvedLibraryDefinitionsFilesMatchTest extends KernelTestBase {
   ];
 
   /**
+   * A list of libraries to skip checking, in the format extension/library_name.
+   *
+   * @var string[]
+   */
+  protected $librariesToSkip = [
+    // Locale has a "dummy" library that does not actually exist.
+    'locale/translations',
+  ];
+
+  /**
    * A list of all paths that have been checked.
    *
    * @var array[]
@@ -136,11 +146,7 @@ protected function verifyLibraryFilesExist($library_definitions) {
     $root = \Drupal::root();
     foreach ($library_definitions as $extension => $libraries) {
       foreach ($libraries as $library_name => $library) {
-        $libraries_to_skip = [
-          // Locale has a "dummy" library that does not actually exist.
-          'locale/translations',
-        ];
-        if (in_array("$extension/$library_name", $libraries_to_skip)) {
+        if (in_array("$extension/$library_name", $this->librariesToSkip)) {
           continue;
         }