How can i import active admin controllers to my active support test?

I want to use this at my test file:

@controller=Admin::PostsController

but it says:

NameError: uninitialized constant Admin::PostsController
    /media/mydata/projects/proj/test/proj_test.rb:23:in `test_activ'

I suppose it has failed to import PostsController. How can I do that?

Note: from rails console I can access:

Admin::PostsController

`Also asked at #stackoverflow: http://stackoverflow.com/questions/32949279/how-can-i-import-active-admin-controllers-to-my-active-support-test

`