Some notes on converting Drupal 7 SimpleTest-based tests to Drupal 8.
Directories and Namespaces
In Drupal 7, SimpleTest-based tests are in the
modulename.test file. This file is expected to contain all test classes. There are no unique namespaces.
Drupal 8 uses namespaced classes to organize code and enable PSR-0/PSR-4 autoloading.
Your test should be in a
Tests namespaces that parallels other namespaced code in your module or project.