I am not sure where to start but let me give you a brief idea on where I am and what I want to achieve. I am quite new to Unit Testing on MVVM and having difficulty on testing t
Your method GetTasksAsync should return a Task so you can actually wait for it.
I recommend this series on Channel9 an specially this episode explaining your problem.
Just to make is clear: Simply changing the signature of GetTasksAsync to
Task GetTasksAsync();
allows you to do this:
var t = GetAsync();
t.Wait();
Assert(...);
In case you really want to test the command in your unit tests and not the actually method called by the command you can use a field in your ViewModel to store the task to await (not so clean) or replace your DelegateCommand by something like described in this post: Awaitable DelegateCommand
Update: In addition to the blog post and considering you are using PRISM, you should have a look a Project Kona from the same team as PRISM. They actually implemented DelegateCommand to support AsyncHandlers