I added the before_filter :login_required authentication within my controllers that require a login for the routes of the specific controllers. After executing the test, I got several errors regarding the routes. The tests have to login during the run.

Let's solve the problem!

(1) The controller

Let me introduce one of my controllers:

class UnitsController < ApplicationController
  before_filter :login_required

  def index
    @units = Unit.all
  end

.....

I added the before_filter :login_required line to require a login for the routes of the controller.

(2) The Fixtures

In the next step, you have to add a user into your users.yml file stored in /test/fixtures.

An example would be:

#password: password
test:
  username: test
  email: test@example.com
  password_hash: 
$2a$10$93UPbJulutAwtfrkEYs0lOH3G6E5ryGBZ9.1EuKFjC9tlEE2JIxXu
  password_salt: $2a$10$93UPbJulutAwtfrkEYs0lO

(3) Adapt the test

You have to tell the test, that he must use the defined fixtures to login during the test.
Add the following lines to your units_controller_test.rb:

require 'test_helper'

class UnitsControllerTest < ActionController::TestCase
  self.use_instantiated_fixtures  = true
  fixtures :users
  
  def setup
    user = User.authenticate('test', 'password')
    if user
      session[:user_id] = user.id
    end
  end

  def teardown
    session[:user_id] = nil
  end

  def test_index
    get :index
    assert_template 'index'
  end

....

You have to add the fixtures, setup and teardown parts to all tests with controllers containing a before_filter :login_required requirement.