Issue #3514774 by dydave: Added basic PHPUNIT Tests coverage for...

https://www.drupal.org/project/admin_toolbar/issues/3514774

Added basic PHPUNIT Tests coverage for admin_toolbar_tools menu links and ToolbarController class:

For each link defined by the module:

• Click on the link to trigger the corresponding method in the ToolbarController class.
• Check the corresponding status message is displayed as expected (no error).