Add a test case

<h4>Summary</h4>

This is to add a test case to check that a foundation slab can be created.

This is to add a test case for the following pull request:
https://github.com/DynamoDS/Dynamo/pull/3347

This is a pull request created based on the following pull request because of recent restructure:
https://github.com/DynamoDS/Dynamo/pull/3372

@pboyer 
PTAL