rails render_to_string problem - ruby-on-rails

Question

I`m trying to test my controller with rspec and always get an error.
users_controller.rb:
def update
#user.update_attributes!(params[:user])
redirect_to #user, :status => 202, :text => render_to_string(:partial => "users/show", :type => "json", :locals => {:user => #user})
#notice, that redirect_to was reinitialized and :text is a parameter for response_body
end
_show.tokamak
user {
id user.id
email user.email
username user.username
}
spec file
it "should NOT update user username" do
username = #user.username
put 'update', :id => #user.id, :user => {:username => username+"abc"}, :format => :json
response.status.should be(202)
response.headers["Location"].length.should be > 0
puts response.body
#user.reload
#user.username.should eq(username)
end
end
So I get an error:
Failure/Error: put 'update', :id =>
#user.id, :user => {:username =>
username+"abc"}, :format => :json
ActionView::Template::Error:
You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.[]
# C:/Users/makaroni4/free_frog/ffapi/app/views/users/_show.tokamak:1:in
_app_views_users__show_tokamak___509498818
_32151168_368311673'
# C:/Users/makaroni4/XXX/XXX/app/controllers/users_controller.rb:22:in
update'
# ./users_controller_spec.rb:34:in
`block (4 levels) in '
So may be I call render_to_string method wrong?

Answer 1

Try stubbing out find?
mock_user = User.stub(:find).with(#user.id) {#user}
To be honest I'd go a few steps further and make sure you mock and stub most of the relevant behavior of the User object (or whatever class #user is). Keep in mind you're only testing that the controller action returns what you expect if you give it valid input--not that the model itself does the right thing.
I had a lot of difficulty wrapping my head around the differences in model vs. controller specs...
I hope this helps...if not, I apologize in advance...
EDIT:
I'll take this a step futher and suggest this test is actually a model test. The actual controller test would be something like as the way your spec test should behave:
it "should NOT update user with invalid input" do
mock_user = mock_model(User, {}).as_null_object
User.stub(:find).with("12") {mock_user}
User.stub(:update_attributes).with({}).and_return(false)
put 'update', :id => "12"
# test that your output is correct, or even if the render target is what you expect.
end