diff -u b/core/modules/system/src/Tests/Module/InstallUninstallTest.php b/core/modules/system/src/Tests/Module/InstallUninstallTest.php
--- b/core/modules/system/src/Tests/Module/InstallUninstallTest.php
+++ b/core/modules/system/src/Tests/Module/InstallUninstallTest.php
@@ -124,7 +124,7 @@
       $this->rebuildContainer();
       if ($name == 'forum') {
         // Forum has an extra step to be able to uninstall it.
-        call_user_func(array($this, 'preUninstallForum'));
+        $this->preUninstallForum();
       }
 
       $now_installed_list = \Drupal::moduleHandler()->getModuleList();
@@ -142,7 +142,7 @@
           if (!empty($has_checkbox) && empty($disabled)) {
             // This one is eligible for being uninstalled.
             $package = $all_modules[$to_uninstall]->info['package'];
-            $this->assertSuccessfullUninstall($to_uninstall, $package);
+            $this->assertSuccessfulUninstall($to_uninstall, $package);
             $added_modules = array_diff($added_modules, array($to_uninstall));
           }
         }
@@ -159,7 +159,7 @@
 
     // Uninstall the help module and put it back into the list of modules.
     $all_modules['help'] = $required_modules['help'];
-    $this->assertSuccessfullUninstall('help', $required_modules['help']->info['package']);
+    $this->assertSuccessfulUninstall('help', $required_modules['help']->info['package']);
 
     // Now that all modules have been tested, go back and try to enable them
     // all again at once. This tests two things: