- * Unlike \Drupal\simpletest\WebTestBase, the modules are only loaded, but not
- * installed. Modules have to be installed manually, if needed.
+ * Tests extending this base class can access services and the database, but the
+ * system is initially empty. This Drupal runs in a minimal mocked filesystem
+ * which operates within vfsStream.
+ *
+ * Modules specified in the $modules property are added to the service container
+ * for each test. The module/hook system is functional. Additional modules
+ * needed in a test should override $modules. Modules specified in this way will
+ * be added to those specified in superclasses.
+ *
+ * Unlike \Drupal\Tests\BrowserTestBase, the modules are not installed. They are
+ * loaded such that their services and hooks are available, but the install
+ * process has not been performed.
+ *
+ * Other modules can be made available in this way using
+ * KernelTestBase::enableModules().
+ *
+ * Some modules can be brought into a fully-installed state using
+ * KernelTestBase::installConfig(), KernelTestBase::installSchema(), and
+ * KernelTestBase::installEntitySchema(). Alternately, tests which need modules
+ * to be fully installed could inherit from \Drupal\Tests\BrowserTestBase.