Add tests to 8.x version - start with existing 7.x tests

Problem/Motivation

The 8.x version doesn't have any tests.

Proposed resolution

Let's start easy -- recreate the tests that exist in 7.x:
https://git.drupalcode.org/project/nodeaccess/tree/7.x-1.x/tests
https://www.drupal.org/docs/8/testing/converting-d7-simpletests-to-drupal-8

Remaining tasks

Patch!

User interface changes

API changes

Data model changes