diff --git a/core/modules/simpletest/src/Tests/SimpleTestTest.php b/core/modules/simpletest/src/Tests/SimpleTestTest.php
index c3758a7..6c49ca7 100644
--- a/core/modules/simpletest/src/Tests/SimpleTestTest.php
+++ b/core/modules/simpletest/src/Tests/SimpleTestTest.php
@@ -173,6 +173,13 @@ function stubTest() {
     catch (\AssertionError $e) {
       $this->assertEqual($e->getMessage(), 'Lorem Ipsum', 'Runtime assertions Enabled and running.');
     }
+    try {
+      assert('FALSE');
+      $this->fail('Runtime assertions are not working.');
+    }
+    catch (\AssertionError $e) {
+      $this->assertEqual($e->getMessage(), 'FALSE', 'Runtime assertions Enabled and running.');
+    }
     // This causes the second of the sixteen passes asserted in
     // confirmStubResults().
     $this->pass($this->passMessage);