Testing e2e

Problem/Motivation

We are missing tests, let's try to setup e2e testing for the Display Builder UX.
Goal is to have e2e tests that can run locally and in ci to avoid big regressions on the UX.

First we evaluate Playwright, then Cypress if needed.
There is an ongoing discussion to replace nightwatch with playwright in core, but seems not so obvious.

Sources to work from:

• Playwright doc
• Playwright tests and code utilities: Automated Testing Kit
• DDev playwright add-on
• Playwright Drupal helpers

Some starting scenarios

Display Builder

• Log in as admin
• Create a generic Display Builder (testing config, all islands enabled)
• Enable / disable islands
• Check it's working

Display Builder usage

Before: login, create DB.

• Open libraries
• Drag a component
• Drag a block in this component (token)
• Set component prop (at least one)
• Set component styles (at least one)
• Set block value
• Set block styles

Other tests

Need to evaluate the benefit of any unit/kernel tests.
Functional and functionalJS could be worth it.

For all cases evaluate Test helpers.