Testing overridden Devise controllers – "No route matches" - ruby-on-rails

Question

I ran rails g devise:controllers users and my routes look like
devise_for :users, controllers: {
sessions: 'sessions'
}
I have a app/controllers/users/sessions_controller that I want to test. My routes look like:
$ rake routes
Prefix Verb URI Pattern Controller#Action
new_user_session GET /users/sign_in(.:format) sessions#new
user_session POST /users/sign_in(.:format) sessions#create
I set up my test like this:
# test/controllers/users/sessions_controller_test.rb
require 'test_helper'
class SessionsControllerTest < ActionController::TestCase
tests Users::SessionsController
test "sign in sanity check" do
user = users(:one)
post :create, email: user.email, password: 'password'
assert_response :success
end
end
Which fails with the error:
ActionController::UrlGenerationError: No route matches {:action=>"create", :controller=>"users/sessions", :email=>"one#example.com", :password=>"password"}
How do I correctly POST to the URL I want? I've tried all sorts of variations, but I'm missing some magic sauce here.

Answer 1

Change your routes.rb to
devise_for :users, controllers: {
sessions: 'users/sessions'
}
And in your test, make sure you have
class SessionsControllerTest < ActionController::TestCase
tests Users::SessionsController
include Devise::TestHelpers
test "sign in sanity check" do
request.env["devise.mapping"] = Devise.mappings[:user]
user = users(:one)
post :create, email: user.email, password: 'password'
assert_response :success
end
end
(You can see how Devise itself does it for an example.)