Incorporate automated tests to the module [#3465346]

The module lacks automated tests for backend functionality.

This module is heavily focused on the frontend, there isn't much to cover with automated tests focusing on the backend, but here are some ideas:

Make sure the Javascript that incorporates all the functionality in this module is being delivered to the page when the module is activated and Drupal TWIG debug mode is activated.
Test these situations for both the front-end and the back-end theme setups.
Ensure the module settings form is loading and accessible as expected for roles granted permission to Administer visual_debugger configuration..

Set up automated tests that can identify any environment changes that might break the module's functionality.

There are no user interface changes being affected by the output of the changes on this issue.

Incorporate automated tests to the module