Apart from the old and more or less deprecated Simpletest, Drupal 8 uses PHPUnit as the testing framework for all types of tests. In this section, we will see how we can work with it to run tests.
On your development environment (or wherever you want to run the tests), make sure you have the composer dependencies installed with the --dev flag. This will include PHPUnit. Keep in mind not to ever do this on your production environment as you can compromise the security of your application.
Although Drupal has a UI interface for running tests, PHPUnit is not well integrated with this. So, it's recommended that we should run them using the command line instead. However, it's actually very easy to do so. To run the entire test suite (of a certain type), we have to navigate to the Drupal core folder:
cd core
Run the following command:
../vendor/bin/phpunit --testsuite...
