Architecture Decision Record: Cypress for functional testing

Context

DPL CMS employs functional testing to ensure the functional integrity of the project.

This is currently implemented using Behat which allows developers to instrument a browser navigating through different use cases using Gherkin, a business readable, domain specific language. Behat is used within the project based on experience using it from the previous generation of DPL CMS.

Several factors have caused us to reevaluate that decision:

• The Drupal community has introduced Nightwatch for browser testing
• Usage of Behat within the Drupal community has stagnated
• Developers within this project have questioned the developer experience and future maintenance of Behat
• Developers have gained experience using Cypress for browser based testing of the React components

Decision

We choose to replace Behat with Cypress for functional testing.

Alternatives considered

There are other prominent tools which can be used for browser based functional testing:

• Playwright: Playwright is a promising tool for browser based testing. It supports many desktop and mobile browsers. It does not have the same widespread usage as Cypress.

Consequences

• Although Cypress supports intercepting requests to external systems this only works for clientside requests. To maintain a consistent approach to mocking both serverside and clientside requests to external systems we integrate Cypress with Wiremock using a similar approach to what we have done with Behat.
• There is a community developed module which integrates Drupal with Cypress. We choose not to use this as it provided limited value to our use case and we prefer to avoid increased complexity.
• We will not only be able to test on mobile browsers as this is not supported by Cypress. We prefer consistency across projects and expected improved developer efficiency over what we expect to be improved complexity of introducing a tool supporting this natively or expanding Cypress setup to support mobile testing.
• We opt not to use Gherkin to describe our test cases. The business has decided that this has not provided sufficient value for the existing project that the additional complexity is not needed. Cypress community plugins support writing tests in Gherkin. These could be used in the future.