Drupal 8 Forms and TDD, part 3: form validation

In part 1, I showed how you can start using TDD when writing Drupal code, and how to apply it to testing a custom file validation callback. In part 2, we tackled testing the form building. In this part, I'll show how you can test the form validation.

I also decided to shoot a quick bonus video with a functional test, to demonstrate the difference in time execution. Food for thought: in our particular example, the functional tests take ~300x longer than the unit tests, without adding any more value. As I mention towards the end, you could probably get that down to “only” 60x times longer, at the cost of maintainability.

Links

• Part 1.
• Part 2.
• Part 4.
• The source code for the example.
• The Composer template for Drupal project used for the project structure.
• The official documentation for writing automated tests in Drupal 8.