Trouble with accessing controller action within nested route with RSpec

Question

I'm working with the following route:

resources :groups, :only => [:show, :create, :update, :destroy] do
    get 'viewmembers' => 'groups#view_members"
end

But when I'm trying to test in RSpec:

describe "GET #viewmembers" do

context "the group members are retrieved" do
    before do
      @group = FactoryGirl.create :group
      ..
      get :viewmembers, group_id: @group.id
    end

    it { should respond_with :ok}
    # others tests...
end

I get the following error:

 Failure/Error: get 'viewmembers', group_id: @group.id

 ActionController::UrlGenerationError:
   No route matches {:action=>"viewmembers", :controller=>"api/v1/groups", :group_id=>"1"}

Is there a different way I should be formulating the GET request in my Rspec test?

Here is what's listed in rake routes:

GET    /api/v1/groups/:group_id/viewmembers(.:format)    api/v1/group#viewmembers{:format=>:json}`

If i take the get 'viewmembers'... route OUT of the nested do-end block for the group resource like so:

resources :groups, :only => [:show, :create, :update, :destroy]
get '/groups/viewmembers' => 'groups#view_members'

then the rspec test runs fine, so it has to be a problem with the way I'm formulating the request...