capybara+rspec erase form text fields - ruby-on-rails

Question

Using capybara+rspec how can i compile a form with empty fields?
I'm testing an edit resource page, so i have a compiled form and want to clean its text fields. This is a partial of test:
context "when submitting" do
before { visit edit_post_path(post) }
it {should have_content('Editing')}
it {current_path.should == edit_post_path(post)}
describe "whit invalid information" do
before do
fill_in "post[title]", :with => "" #not working
fill_in "post[body]", :with => "" #not working
click_button "update"
end
it {current_path.should == edit_post_path(post)}
end
describe "whit valid information" do
before do
fill_in "post[title]", with: "some"
fill_in "post[body]", with: "some"
click_button "update"
end
it {should have_content('some')}
it {should have_content('some')}
it {current_path.should == post_path(post)}
end
end

Answer 1

Check manually actual ID/name/label of relevant field in generated HTML of Edit-page via Chrome:InspectElement of Firefox:Firebug. High chances they are different to "post[title]".
UPD. Try to fill in empty strings manually on the page. Does it work fine? I mean error displayed and the route is correct. Firing "Update"-button and getting an error you're not on the edit_post_path anymore. It happens bc in case of unsuccessful #post.update you're rendering Post#edit-view from Post#update action.

Answer 2

Likely problem is that post[title] and post[body] are the names of the fields, and not the IDs.
Also, something you might want to look into to make your tests a little more rigorous: capybara has a builtin within function that yields a block in which you can perform more actions. Check out the documentation on the front page of the gem page: https://github.com/jnicklas/capybara. It would probably look something like:
describe "whit invalid information" do
before do
within("#post") do
fill_in "title", :with => ""
fill_in "body", :with => ""
click_button "update"
end
end
it {current_path.should == edit_post_path(post)}
end