Add new service to ServiceContainer
MediaWikiServices::getInstance()->getHookRunner()
for
\MediaWiki\HookContainer\ProtectedHookAccessorTrait::getHookRunner
protected function getHookRunner() {
return new HookRunner( $this->getHookContainer() );
}to simple test mocked hook methods
This not going to work as extension should create own HookRunner. It is recommended to create the HookRunner where needed as the class is a simple and cheap to create. That is also the used pattern all over in core.
There is no need to create global service here. Would suggest to decline this task.