Change record status: 
Project: 
Introduced in branch: 
8.6.x
Introduced in version: 
8.6.0
Description: 

\Drupal\simpletest\InstallerTestBase has been deprecated in favor of \Drupal\FunctionalTests\Installer\InstallerTestBase.

All setUp() logic should be moved to prepareEnvironment() to take into account the order in which the file system is set up in BrowserTestBase.

Also see #2907728: Installer: Convert system functional tests to phpunit.

Impacts: 
Module developers