Creates storage objects for each collection defined for this class.
Storing the storage objects in a class member variable causes a fatal exception in DatabaseStorageExpirableTest, because in that situation garbage collection is not triggered until the test class itself is destructed, after tearDown() has deleted the database tables. Instead, create the storage objects locally in each test using this method.
Drupal\system\Tests\KeyValueStore\DatabaseStorageExpirable
Drupal\Core\KeyValueStore\DatabaseStorageExpirable::garbageCollection()
protected function createStorage() {
$stores = array();
foreach ($this->collections as $i => $collection) {
$stores[$i] = $this->container
->get($this->factory)
->get($collection);
}
return $stores;
}