diff --git a/core/tests/Drupal/KernelTests/Core/Theme/StableDecoupledTest.php b/core/tests/Drupal/KernelTests/Core/Theme/StableDecoupledTest.php
index 94e4e00..06bc524 100644
--- a/core/tests/Drupal/KernelTests/Core/Theme/StableDecoupledTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Theme/StableDecoupledTest.php
@@ -7,9 +7,9 @@
 /**
  * Tests that themes do not depend on Stable assets.
  *
- * These tests exist to facilitate the process of decoupling theme from Stable.
+ * These tests exist to facilitate the process of decoupling themes from Stable.
  * The decoupling process includes:
- *   1. Identifying Stable assets that differ from core ones
+ *   1. Identifying Stable assets that differ from core ones.
  *   2. Of those differing assets, identify those that are inherited by
  *     the themes being tested.
  *   3. Determine if a copy of that Stable asset must be added to the theme,
@@ -20,6 +20,13 @@
  * asset, or it being determined that it's acceptable for the theme to use
  * core's version (in which case it will be skipped by this test).
  *
+ * If any bug fixes require changes to core assets, the front end backwards
+ * compatibiltiy policy states that Stable should not be changed. Therefore, bug
+ * fixes that touch core assets will most likely need to update this test to add
+ * the changed core asset to the list of ignored/skipped assets. See the
+ * 'to-skip' subarray for each core theme in the providerTestDecoupledStable()
+ * data provider.
+ *
  * @group Theme
  */
 class StableDecoupledTest extends KernelTestBase {
@@ -71,8 +78,8 @@ protected function assetsThatDifferInStable() {
     // Assets that are in core but not Stable.
     $in_core_only = array_diff(array_keys($core_assets), array_keys($stable_assets));
 
-    // Files that are included in Stable but never loaded by core themes. This
-    // files file.admin.css and filter.admin.css were removed in core so
+    // Files that are included in Stable but never loaded by core themes. The
+    // files file.admin.css and filter.admin.css were removed in core, so
     // Stable's libraries-override never replaces them with core's version. The
     // simpletest-result-summary.html.twig template is skipped because the
     // Simpletest module was removed from core.
@@ -174,14 +181,18 @@ public function testDecoupledStable($path, array $to_skip) {
     // tested as that means they're already overridden. Also exclude those
     // listed in $to_skip.
     $files_inherited_from_stable = array_diff($files_to_check, array_keys($assets), $to_skip);
-    $this->assertEmpty($files_inherited_from_stable);
+    $this->assertEmpty($files_inherited_from_stable, 'There should be no assets inhereted from Stable, but the following files are inhereted: ' . var_export(array_values($files_inherited_from_stable), TRUE));
   }
 
   /**
-   * Data provider.
+   * Provides data for testDecoupledStable().
    *
    * The to-skip arrays should become increasingly smaller as issues that
-   * address Stable library dependencies are completed.
+   * address Stable library dependencies are completed. However, they will grow
+   * if bugs are fixed in core assets in the 9.0.x branch. In those cases, we
+   * have to leave Stable alone, but the difference between the stable and core
+   * asset will be flagged as a test failure and we'll need to add those files
+   * to the to-skip lists.
    *
    * @return array[]
    *   Themes and the asset filenames to be ignored.