diff --git a/core/modules/simpletest/simpletest.module b/core/modules/simpletest/simpletest.module
index dbd2a9aafac296a34cadebe0abd925217c6fde76..ed3641239c807224aa9906ee95eb61c8babce359 100644
--- a/core/modules/simpletest/simpletest.module
+++ b/core/modules/simpletest/simpletest.module
@@ -11,7 +11,6 @@
 use Drupal\Core\File\Exception\FileException;
 use Drupal\Core\Render\Element;
 use Drupal\Core\Routing\RouteMatchInterface;
-use Drupal\simpletest\TestBase;
 use Drupal\Core\Test\TestDatabase;
 use Drupal\simpletest\TestDiscovery;
 use Drupal\Tests\Listeners\SimpletestUiPrinter;
@@ -552,11 +551,11 @@ function simpletest_log_read($test_id, $database_prefix, $test_class) {
           'line' => $match[4],
           'file' => $match[3],
         ];
-        TestBase::insertAssert($test_id, $test_class, FALSE, $match[2], $match[1], $caller);
+        simpletest_insert_assert($test_id, $test_class, FALSE, $match[2], $match[1], $caller);
       }
       else {
         // Unknown format, place the entire message in the log.
-        TestBase::insertAssert($test_id, $test_class, FALSE, $line, 'Fatal error');
+        simpletest_insert_assert($test_id, $test_class, FALSE, $line, 'Fatal error');
       }
       $found = TRUE;
     }
@@ -564,6 +563,62 @@ function simpletest_log_read($test_id, $database_prefix, $test_class) {
   return $found;
 }
 
+/**
+ * Store an assertion from outside the testing context.
+ *
+ * This is useful for inserting assertions that can only be recorded after
+ * the test case has been destroyed, such as PHP fatal errors. The caller
+ * information is not automatically gathered since the caller is most likely
+ * inserting the assertion on behalf of other code. In all other respects
+ * the method behaves just like \Drupal\simpletest\TestBase::assert() in terms
+ * of storing the assertion.
+ *
+ * @param string $test_id
+ *   The test ID to which the assertion relates.
+ * @param string $test_class
+ *   The test class to store an assertion for.
+ * @param bool|string $status
+ *   A boolean or a string of 'pass' or 'fail'. TRUE means 'pass'.
+ * @param string $message
+ *   The assertion message.
+ * @param string $group
+ *   The assertion message group.
+ * @param array $caller
+ *   The an array containing the keys 'file' and 'line' that represent the file
+ *   and line number of that file that is responsible for the assertion.
+ *
+ * @return
+ *   Message ID of the stored assertion.
+ */
+function simpletest_insert_assert($test_id, $test_class, $status, $message = '', $group = 'Other', array $caller = []) {
+  // Convert boolean status to string status.
+  if (is_bool($status)) {
+    $status = $status ? 'pass' : 'fail';
+  }
+
+  $caller += [
+    'function' => 'Unknown',
+    'line' => 0,
+    'file' => 'Unknown',
+  ];
+
+  $assertion = [
+    'test_id' => $test_id,
+    'test_class' => $test_class,
+    'status' => $status,
+    'message' => $message,
+    'message_group' => $group,
+    'function' => $caller['function'],
+    'line' => $caller['line'],
+    'file' => $caller['file'],
+  ];
+
+  return TestDatabase::getConnection()
+    ->insert('simpletest')
+    ->fields($assertion)
+    ->execute();
+}
+
 /**
  * Gets a list of all of the tests provided by the system.
  *
diff --git a/core/modules/simpletest/src/TestBase.php b/core/modules/simpletest/src/TestBase.php
index ef886c07688b429d7d7f2a6e536543a1684f43b7..4fce148cf1c40171b843ef59e8feb13ce1836b4c 100644
--- a/core/modules/simpletest/src/TestBase.php
+++ b/core/modules/simpletest/src/TestBase.php
@@ -384,6 +384,10 @@ protected function assert($status, $message = '', $group = 'Other', array $calle
    * @return
    *   Message ID of the stored assertion.
    *
+   * @deprecated in Drupal 8.8.0 and will be removed before Drupal 9.0.0. Use
+   *   simpletest_insert_assert() instead.
+   *
+   * @see https://www.drupal.org/node/3030340
    * @see \Drupal\simpletest\TestBase::assert()
    * @see \Drupal\simpletest\TestBase::deleteAssert()
    */
diff --git a/core/scripts/run-tests.sh b/core/scripts/run-tests.sh
index 41495c779eb47d74a1c7e8252e837cefb57cb06a..f08956e61fc44a478b72908330a1754e5c2c53ac 100755
--- a/core/scripts/run-tests.sh
+++ b/core/scripts/run-tests.sh
@@ -747,7 +747,7 @@ function simpletest_script_execute_batch($test_classes) {
           // @see https://www.drupal.org/node/2780087
           $total_status = max(SIMPLETEST_SCRIPT_EXIT_FAILURE, $total_status);
           // Insert a fail for xml results.
-          TestBase::insertAssert($child['test_id'], $child['class'], FALSE, $message, 'run-tests.sh check');
+          simpletest_insert_assert($child['test_id'], $child['class'], FALSE, $message, 'run-tests.sh check');
           // Ensure that an error line is displayed for the class.
           simpletest_script_reporter_display_summary(
             $child['class'],
@@ -950,7 +950,7 @@ function simpletest_script_cleanup($test_id, $test_class, $exitcode) {
     // would also delete file directories of other tests that are potentially
     // running concurrently.
     try {
-      \Drupal::service('file_system')->deleteRecursive($test_directory, ['Drupal\simpletest\TestBase', 'filePreDeleteCallback']);
+      \Drupal::service('file_system')->deleteRecursive($test_directory, ['\Drupal\Tests\BrowserTestBase', 'filePreDeleteCallback']);
       $messages[] = "- Removed test site directory.";
     }
     catch (FileException $e) {