extraño error de rspec `método indefinido model_name`

I've searched around and found this issue with other questions, but my app works completely, it's just my tests that are throwing the error.

_formulario.html.haml

= simple_form_for @employer_profile do |f|
 =f.error_notification

.form-inputs
  =f.input :company_name
...


.form-actions
  =f.button :submit, 'Create Employer profile', id: 'employer-profile-submit'

I don't even know what other code to paste, I've not defined model_name anywhere in the app, nothing is nil in any views or in my tests when I check for stuff.

error completo

1) Creating Employer Profiles Employer Profile edits a profile
 Failure/Error: visit employer_profiles_edit_path(@user)
 ActionView::Template::Error:
   undefined method `model_name' for NilClass:Class
 # ./app/views/employer_profiles/_form.html.haml:1:in     `_app_views_employer_profiles__form_html_haml__754845775744985234_44321300'
 # ./app/views/employer_profiles/edit.html.haml:4:in `_app_views_employer_profiles_edit_html_haml__3107954110108075276_44064480'
 # ./spec/features/employer_profiles_spec.rb:44:in `block (3 levels) in <top (required)>'

employer_profile_controller.rb

    class EmployerProfilesController < ApplicationController
  before_filter :set_user

  def new
    @employer_profile = EmployerProfile.new(user_id: @user.id)
  end

  def show
    @employer_profile = EmployerProfile.find_by_user_id(params[:user_id])
  end

  def edit
    @employer_profile = EmployerProfile.find_by_user_id(params[:user_id])
  end

  def create
    @employer_profile = EmployerProfile.new(employer_profile_params)

    respond_to do |format|
      if @employer_profile.save
        format.html { redirect_to employer_profile_path(@user), notice: 'Listing was successfully created.' }
        format.json { render action: 'show', status: :created, location: employer_profile_path(@user) }
      else
        format.html { render action: 'new' }
        format.json { render json: @employer_profile.errors, status: :unprocessable_entity }
      end
    end
  end

  def update
    @employer_profile = EmployerProfile.find_by_user_id(params[:user_id])

    respond_to do |format|
      if @employer_profile.update(employer_profile_params)
        format.html { redirect_to employer_profile_path(@user), notice: 'Employer Profile was successfully updated.' }
        format.json { head :no_content }
      else
        format.html { render action: 'edit' }
        format.json { render json: @employer_profile.errors, status: :unprocessable_entity }
      end
    end

  end

  private

  def set_user
    @user = current_user
  end
  def employer_profile_params
    params.require(:employer_profile).permit(:company_name, :employer_rating, :description, :website, :city, :state, :email, :address, :zip, :industry).merge!(:user_id => @user.id)
  end

end

edit: I think I may have pinned this weirdness down to a simple_form thing. I used a regular form_for and I don't seem to be getting the error for now.

employer_profile_feature_spec.rb

require 'spec_helper'
include Warden::Test::Helpers
Warden.test_mode!

  def login_user
    before(:each) do
      @user = FactoryGirl.create(:user)
      login_as(@user)
    end 
  end 


feature "Creating Employer Profiles" do

  login_user

  describe 'Employer Profile' do
    describe 'create profile' do
      it 'completes a profile and shows the results' do
        visit '/' 
        expect{
          click_link('New Employer Profile')
            fill_in 'Company name', with: 'Lost Tie LLC'
            fill_in 'Employer rating', with: 1
            fill_in 'Description', with: 'testing text'
            fill_in 'City', with: 'test-city'
            fill_in 'State', with: 'test-state'
            fill_in 'Email', with: 'test@example.com'
            fill_in 'Website', with: 'www.example.com'
            fill_in 'Address', with: '123 example street'
            fill_in 'Zip', with: 12345
            fill_in 'Industry', with: 'Oil'
          click_button 'Create Employer profile'
        }.to change(EmployerProfile,:count).by(1)

        page.should have_content 'Lost Tie LLC'
      end 
    end 

    it "edits a profile" do
      visit employer_profiles_edit_path(@user)
      expect(EmployerProfile.find_by_user_id(params[:user_id])).to_not be_nil
    end 

rutas de rastrillo

  employer_profiles_new GET    /employer_profiles/new(.:format)           employer_profiles#new
       employer_profiles POST   /employer_profiles(.:format)               employer_profiles#create
        employer_profile GET    /employer_profile/:user_id(.:format)       employer_profiles#show
  employer_profiles_edit GET    /employer_profiles/:user_id/edit(.:format) employer_profiles#edit
                         PUT    /employer_profiles/:user_id(.:format)      employer_profiles#update