[SalesForce] Send email notification for “Completed” Tasks to Task Creator

David, have you tried setting the SeeAllData modifier to true for your test class?

I tried out your code, and it appears that in order for you to validate that the ActivityHistory table was populated, you need start your test class with this: @isTest(SeeAllData = true)

First of all, the feature Tasks to a Queue doesn't exist. But there is a highly voted on Idea that you should upvote

In the comments thread, there is a workaround that you could consider:

We added a role that reports up to the role(s) that respond to tasks, and put a dummy Customer Service user into that role. New tasks are assigned to this dummy user, and it acts as a queue. As a higher-up, a customer service rep can reassign the tasks from the dummy user to themselves, or if you are a manager, to others.

Alternately, you can create sharing rules that explicitly grant access to the objects the distributed tasks will be associated with. People are notified of incoming activity/new tasks because the dummy user's email is set to something like customer_service@mycompany.com. Folks on the email list respond appropriately. You could also automate it with a workflow rule that emails a specific group upon task creation. This requires a spare license and of course, YMMV. Hope this is helpful!

-- James Snavely