At the end of May, I made an initiative to move all of the Drupal Commerce tests away from Simpletest and to use the available test classes built off of PHPUnit. Why? Simpletest is a test framework within Drupal and not used by the PHP community at large.

With the KernelTestBaseTNG™ issue, Drupal core officially moved to being based on top of PHPUnit for Kernel and Unit tests. Soon more test types were to follow, such as browser tests and JavaScript testing.

Death to Simpletest, Long Live PHPUnit, Mink, and PhantomJS

We now have PHPUnit as our test framework, the choice of the greater PHP community. The browser tests use the Mink browser emulator, which anyone working with Behat should be somewhat familiar. Testing JavaScript is done by pointing PhantomJS configuration to Mink. No longer are we limited to the functionalities of Simpletest and our community to develop it.