Automated Tests Help Validate Drupal Module Update Hooks

Testing Drupal module update hooks can require fixtures because the stored data before an update may no longer match a module’s current schema. James Shields explains this problem in Creating Tests for Drupal Module Update Hooks, using an update path from the Smart Trim module as the example. The post is aimed at maintainers who need repeatable checks for schema or configuration changes on existing installations.

The example update hook moves “read more” link settings into a nested more array across entity view displays that use Smart Trim. James notes that manual testing is awkward because each run changes the database, making local reset tools such as ddev snapshot useful during development. For automated coverage, he recommends creating a fixture from an installed Drupal site running the module version before the update hook, dumping it with core/scripts/db-tools.php and dump-database-d8-mysql, and storing the compressed file under tests/fixtures/update/.

The tutorial then loads the fixture through a functional update test based on Drupal\FunctionalTests\Update\UpdatePathTestBase and setDatabaseDumpFiles(). The test creates an administrative user, calls $this->runUpdates(), and asserts that the migrated configuration matches the expected structure. James also covers fixture maintenance when Drupal versions move forward, including importing an older dump, running updates, creating a newer fixture, and selecting fixture files with \Drupal::VERSION for Drupal 10, Drupal 11, or later test targets.