Routeing error in Controller_specs in active_admin

Routeing error in Controller_specs in active_admin

I've set up some specs to test my active admin controllers.
it "assigns the requested blog to @blog" do
@blog = FactoryGirl.create(:blog)
get :show, id: @blog
assigns(:blog).should eq(@blog)
end
when I run this spec file separately it's all green, but when I run all my
specs I get this error.
Failure/Error: get :show, :id => @blog
ActionView::Template::Error:
No route matches {:id=>#<User id: nil, role: nil, phone: nil,
name: nil, firm_id: nil, hourly_rate: nil, loginable_type: nil,
loginable_id: nil, loginable_token: nil, created_at: nil,
updated_at: nil, avatar_file_name: nil, avatar_content_type:
nil, avatar_file_size: nil, avatar_updated_at: nil, email: "",
encrypted_password: "", reset_password_token: nil,
reset_password_sent_at: nil, remember_created_at: nil,
sign_in_count: 0, current_sign_in_at: nil, last_sign_in_at:
nil, current_sign_in_ip: nil, last_sign_in_ip: nil>,
:controller=>"admin/blogs", :action=>"edit", :format=>nil}
missing required keys: [:id]
Any ideas what's worng?