Failures:

  1) DevicesController device#update is handled
     Failure/Error: patch :update, params: { device: @device }

     ActionController::UrlGenerationError:
       No route matches {:action=>"update", :controller=>"devices", :device=>#<Device id: 3, token: "Xn/6ut68w", nickname: "rough-snowflake-470", network: nil, ip_address: nil, gateway: nil, version: nil, ips_scan: nil, ips_exclude: nil, user_id: 3, created_at: "2018-02-21 02:44:16", updated_at: "2018-02-21 02:44:16">}

RSpec.describe DevicesController, type: :controller do

  before(:each) { @user = User.create(email: 'test@test.com', password: 'password', password_confirmation: 'password') }

  it 'device#update is handled' do
    sign_in(@user)
    @device = @user.devices.first
    patch :update, params: { device: @device }
    @device.reload
    expect(response.status).to eq(200)
  end
end

class DevicesController < ApplicationController
  before_action :set_device, only: %i[edit show update]
  respond_to :html

  def update
    if @device.update(device_params)
      flash[:notice] = 'Successful update'
      respond_with :edit, :device
    else
      flash[:warning] = 'Address formats allowed: x.x.x.x OR x.x.x.x-x OR x.x.x.x/x'
      respond_with :edit, :device
    end
  end

  private def set_device
    @device = Device.find(params[:id])
  end

  private def device_params
    params.require(:device).permit(:token, :nickname, :ips_scan, :ips_exclude)
  end
end

patch :update, params: { device: @device, nickname: 'foobar' }

$ rake routes
  edit_device GET    /devices/:id/edit(.:format)    devices#edit
       device GET    /devices/:id(.:format)         devices#show
              PATCH  /devices/:id(.:format)         devices#update
              PUT    /devices/:id(.:format)         devices#update