Confirm there is a test that procedural preprocess functions are executed properly in modules

Problem/Motivation

There are test procedural functions in module_test_procedural
We should ensure that there is a test most likely in core/tests/Drupal/KernelTests/Core/Theme/RegistryTest.php
that confirms these functions are picked up and that they are executed.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet