diff --git a/core/tests/Drupal/Tests/ComposerIntegrationTest.php b/core/tests/Drupal/Tests/ComposerIntegrationTest.php
index 4557e94..f405be8 100644
--- a/core/tests/Drupal/Tests/ComposerIntegrationTest.php
+++ b/core/tests/Drupal/Tests/ComposerIntegrationTest.php
@@ -7,9 +7,19 @@
 
 namespace Drupal\Tests;
 
+use Drupal\Tests\UnitTestCase;
+
 /**
  * Tests Composer integration.
  *
+ * Currently, Drupal requires composer.json files to be in specific places so
+ * that we can test their validity and integrity. This test could fail if the
+ * shipped Drupal 8 file system is modified.
+ *
+ * You can run tests from PHPUnit with --exclude-group Composer in order to
+ * avoid these test fails. You can also add a dummy empty composer.json file:
+ * "{}" to your installation's root directory for other testing needs.
+ *
  * @group Composer
  */
 class ComposerIntegrationTest extends UnitTestCase {