Rspec test to post as json - ruby-on-rails

Question

I am having problems trying to post as JSON to my controller action within my rspec test
RSpec.describe RegistrationsController, type: :controller do
context 'Adding a Valid User' do
it 'Returns Success Code and User object' do
#params = { :user => {username: 'name', school: 'school'} }.to_json
post :create, #params
end
end
end
At the moment I want to get a successful post request firing but am getting this error back all the time
Failure/Error: post :create, #params
AbstractController::ActionNotFound:
Could not find devise mapping for path "/lnf".
My routes are setup like so
Rails.application.routes.draw do
constraints(subdomain: 'api') do
devise_for :users, path: 'lnf', controllers: { registrations: "registrations" }
devise_scope :user do
post "/lnf" => 'registrations#create'
end
end
end
Rake routes outputs the following
Prefix Verb URI Pattern Controller#Action
user_registration POST /lnf(.:format) registrations#create {:subdomain=>"api"}
lnf POST /lnf(.:format) registrations#create {:subdomain=>"api"}
So i have 2 declarations for the same action?
Could anyone shed some light on this please
Thanks

Answer 1

Ok so after a painstaking few hours i have got my tests passing correctly and posting as json by doing the following
require 'rails_helper'
RSpec.describe RegistrationsController, type: :controller do
before :each do
request.env['devise.mapping'] = Devise.mappings[:user]
end
context 'Adding a Valid User' do
it 'Returns Success Code and User object' do
json = { user: { username: "richlewis14", school: "Baden Powell", email: "richlewis14#gmail.com", password: "Password1", password_confirmation: "Password1"}}.to_json
post :create, json
expect(response.code).to eq('201')
end
end
end
My Routes are back to normal
Rails.application.routes.draw do
constraints(subdomain: 'api') do
devise_for :users, path: 'lnf', controllers: { registrations: "registrations" }
end
end
And in my test environment I had to add
config.action_mailer.default_url_options = { host: 'localhost' }
The key here was
request.env['devise.mapping'] = Devise.mappings[:user]
Not fully sure as yet to what it does, its next on my list to find out, but my tests are starting to run and pass