https://api.drupal.org/api/drupal/core%21lib%21Drupal%21Core%21Test%21FunctionalTestSetupTrait.php/property/FunctionalTestSetupTrait%3A%3ArootUser/main
FunctionalTestSetupTrait::$rootUser | Drupal API
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https://api.drupal.org/api/drupal/core%21lib%21Drupal%21Core%21Test%21FunctionalTestSetupTrait.php/property/FunctionalTestSetupTrait%3A%3ArootUser/8.9.x
FunctionalTestSetupTrait::$rootUser | Drupal API
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