diff -u b/core/modules/system/system.install b/core/modules/system/system.install
--- b/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -2243,6 +2243,15 @@
 }
 
 /**
+ * Move the file_public_path variable to settings.
+ */
+function system_upgrade_8060() {
+  if ($path = update_variable_get('file_public_path')) {
+    drupal_rewrite_settings(array('settings' => array('file_public_path' => $path)));
+  }
+}
+
+/**
  * @} End of "defgroup updates-7.x-to-8.x".
  * The next series of updates should start at 9000.
  */
diff -u b/core/scripts/run-tests.sh b/core/scripts/run-tests.sh
--- b/core/scripts/run-tests.sh
+++ b/core/scripts/run-tests.sh
@@ -3,6 +3,7 @@
  * @file
  * This script runs Drupal tests from command line.
  */
+use Drupal\Core\StreamWrapper\PublicStream;
 
 const SIMPLETEST_SCRIPT_COLOR_PASS = 32; // Green.
 const SIMPLETEST_SCRIPT_COLOR_FAIL = 31; // Red.
@@ -398,7 +399,7 @@
           echo 'FATAL ' . $child['class'] . ': test runner returned a non-zero error code (' . $status['exitcode'] . ').' . "\n";
           if ($args['die-on-fail']) {
             list($db_prefix, ) = simpletest_last_test_get($child['test_id']);
-            $public_files = file_public_path();
+            $public_files = PublicStream::basePath();
             $test_directory = $public_files . '/simpletest/' . substr($db_prefix, 10);
             echo 'Simpletest database and files kept and test exited immediately on fail so should be reproducible if you change settings.php to use the database prefix '. $db_prefix . ' and config directories in '. $test_directory . "\n";
             $args['keep-results'] = TRUE;
@@ -567,7 +568,7 @@
 
   // Check whether a test file directory was setup already.
   // @see prepareEnvironment()
-  $public_files = file_public_path();
+  $public_files = PublicStream::basePath();
   $test_directory = $public_files . '/simpletest/' . substr($db_prefix, 10);
   if (is_dir($test_directory)) {
     // Output the error_log.