undefined method 'body' for nil:Nilclass - ruby-on-rails

Question

I am writing integration test for my application. For the following test, I am getting
undefined method 'body' for nil:Nilclass
My RSpec code:
it "should not make a new user" do
visit signup_path
fill_in "Name", :with => ""
fill_in "Email", :with => ""
fill_in "Password", :with => ""
fill_in "Confirmation", :with => ""
click_button "Sign up"
response.should render_template('users/new')
response.should have_selector("div#error_explanation")
end
Controller:
class UsersController < ApplicationController
def new
#user = User.new
#title = "Sign Up"
end
def show
#user = User.find(params[:id])
#title = #user.name
end
def create
#user = User.new(user_params)
if #user.save
# Handle a successful save.
flash[:success] = "Welcome to the Sample App!"
redirect_to #user
else
#title = "Sign Up"
render 'new'
end
end
def user_params
params.require(:user).permit(:name, :email, :password, :password_confirmation)
end
end
test.log:
[1m[36mActiveRecord::SchemaMigration Load (0.0ms)[0m [1mSELECT "schema_migrations".* FROM "schema_migrations"[0m [1m[35m (0.0ms)[0m begin transaction
Started GET "/signup" for 127.0.0.1 at 2015-05-06 19:22:35 +0530
Processing by UsersController#new as HTML
Rendered shared/_error_messages.html.erb (46.8ms)
Rendered users/new.html.erb within layouts/application (93.6ms)
Rendered layouts/_stylesheets.html.erb (15.6ms)
Rendered layouts/_header.html.erb (0.0ms)
Rendered layouts/_footer.html.erb (0.0ms)
Completed 200 OK in 203ms (Views: 140.4ms | ActiveRecord: 0.0ms)
Started POST "/users" for 127.0.0.1 at 2015-05-06 19:22:36 +0530
Processing by UsersController#create as HTML
Parameters: {"utf8"=>"✓", "user"=>{"name"=>"", "email"=>"", "password"=>"[FILTERED]", "password_confirmation"=>"[FILTERED]"}, "commit"=>"Sign up"}
[1m[36m (0.0ms)[0m [1mSAVEPOINT active_record_1[0m
[1m[35mUser Exists (0.0ms)[0m SELECT 1 AS one FROM "users" WHERE LOWER("users"."email") = LOWER('') LIMIT 1
[1m[36m (0.0ms)[0m [1mROLLBACK TO SAVEPOINT active_record_1[0m
Rendered shared/_error_messages.html.erb (0.0ms)
Rendered users/new.html.erb within layouts/application (0.0ms)
Rendered layouts/_stylesheets.html.erb (0.0ms)
Rendered layouts/_header.html.erb (15.6ms)
Rendered layouts/_footer.html.erb (0.0ms)
Completed 200 OK in 47ms (Views: 15.6ms | ActiveRecord: 0.0ms)
[1m[35m (0.0ms)[0m rollback transaction
Error:
5 errors prohibited this user from being saved:
There were problems with the following fields:
Name can't be blank
Email can't be blank
Email is invalid
Password can't be blank
Password is too short (minimum is 6 characters)
What is missing/wrong in this code?