diff -u b/core/modules/simpletest/src/WebTestBase.php b/core/modules/simpletest/src/WebTestBase.php
--- b/core/modules/simpletest/src/WebTestBase.php
+++ b/core/modules/simpletest/src/WebTestBase.php
@@ -830,8 +830,6 @@
     // proper session cookies were set on a response. Because the child site
     // uses the same session name as the test runner, it is necessary to make
     // that available to test-methods.
-    // @todo: Introduce a setting such that the session name can be customized
-    // for the child site.
     $this->session_name = $this->originalSessionName;
 
     // Reset the static batch to remove Simpletest's batch operations.