How can I set Magento 2 locale programmatically
You can use localeInterface to set Magento 2 locale programmatically.
$objectManager = \Magento\Framework\App\ObjectManager::getInstance();
$localeInterface = $objectManager->create('Magento\Framework\Locale\ResolverInterface');
$localeInterface->setLocale('en_AU');
$localeInterface->setDefaultLocale('en_AU');