https://github.com/cerebris/jsonapi-resources/issues/954

jr_bug_reproducing_954.rb

begin
  require 'bundler/inline'
rescue LoadError => e
  STDERR.puts 'Bundler version 1.10 or later is required. Please update your Bundler'
  raise e
end

gemfile(true) do
  source 'https://rubygems.org'

  gem 'rails', '4.2.7', require: false
  gem 'sqlite3', platform: :mri

  gem 'activerecord-jdbcsqlite3-adapter', platform: :jruby

  # gem 'jsonapi-resources', '0.8.0', require: false
  # gem 'jsonapi-resources', require: false
  gem 'jsonapi-resources', git: 'https://github.com/cerebris/jsonapi-resources', require: false
end

# prepare active_record database
require 'active_record'

ActiveRecord::Base.establish_connection(adapter: 'sqlite3', database: ':memory:')
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  # Add your schema here
  create_table :storages, force: true do |t|
    t.string :token, null: false
    t.string :name
    t.timestamps null: false
  end

  create_table :keepers, force: true do |t|
    t.string :name
    t.integer :storage_id
  end
end

# create models
class Storage < ActiveRecord::Base
  has_one :keeper
end

class Keeper < ActiveRecord::Base
  belongs_to :storage
end

# prepare rails app
require 'action_controller/railtie'
# require 'action_view/railtie'
require 'jsonapi-resources'

class ApplicationController < ActionController::Base
end

# prepare jsonapi resources and controllers
class JsonApiController < ApplicationController
  include JSONAPI::ActsAsResourceController
end

class StoragesController < JsonApiController
end

class KeepersController < JsonApiController
end

class StorageResource < JSONAPI::Resource
  attribute :name
end

class KeeperResource < JSONAPI::Resource
  has_one :storage
  attribute :name

  def self.updatable_fields(_context)
    super - [:storage]
  end
end

class TestApp < Rails::Application
  config.root = File.dirname(__FILE__)
  config.logger = Logger.new(STDOUT)
  Rails.logger = config.logger

  secrets.secret_token = 'secret_token'
  secrets.secret_key_base = 'secret_key_base'

  config.eager_load = false
end

# initialize app
Rails.application.initialize!

JSONAPI.configure do |config|
  config.json_key_format = :underscored_key
  config.route_format = :underscored_key
  config.raise_if_parameters_not_allowed = false
end

# draw routes
Rails.application.routes.draw do
  jsonapi_resources :keepers, only: [:show, :update]
end

# prepare tests
require 'minitest/autorun'
require 'rack/test'

# Replace this with the code necessary to make your test fail.
class BugTest < Minitest::Test
  include Rack::Test::Methods

  def response_json
    JSON.parse(last_response.body) rescue nil
  end

  def pretty_response_json
    JSON.pretty_generate(response_json) rescue nil
  end

  def json_api_headers
    {'Accept' => JSONAPI::MEDIA_TYPE, 'CONTENT_TYPE' => JSONAPI::MEDIA_TYPE}
  end

  def test_keeper_update_storage
    storage = Storage.create! name: 'Warehouse 1', token: 'some-token'
    keeper = Keeper.create! name: 'John Doe', storage: storage
    refute_nil keeper.storage
    update_json = {
        data: {
            anything: 'really'
        }
    }
    patch "/keepers/#{keeper.id}/storage", update_json.to_json, json_api_headers
    puts pretty_response_json
    assert_equal 404, last_response.status
    refute_nil keeper.storage
  end

  private

  def app
    Rails.application
  end
end