TypeError: can't cast ActionController::Parameters to integer Error code when testing controller in Rails 4.1.10

I'm trying to learn how to test Rails controllers right now and I'm stuck. Whenever I try to test my test/controllers/articles_controller_test.rb file I get this error message.

  ArticlesControllerTest#test_should_update_article:
  TypeError: can't cast ActionController::Parameters to integer
    app/controllers/articles_controller.rb:67:in `update'
    test/controllers/articles_controller_test.rb:50:in `block in <class:ArticlesControllerTest>'

The articles_controller_test.rb file is this:

require 'test_helper'

class ArticlesControllerTest < ActionController::TestCase
  setup do
    @article = articles(:welcome_to_rails)
  end

  test "should get index" do
    get :index
    assert_response :success
    assert_template 'index'
    assert_not_nil assigns(:articles)
  end

  test "should get new" do
    login_as(:eugene)
    get :new
    assert_response :success
  end

  test "should create article" do
    login_as(:eugene)
    assert_difference('Article.count') do
      post :create, :article => { :title => 'Post title',
                                  :body => 'Lorem ipsum..' }
    end

    assert_response :redirect
    assert_redirected_to article_path(assigns(:article))
  end

  test "should show article" do
    get :show, :id => @article.to_param

    assert_response :success
    assert_template 'show'

    assert_not_nil assigns(:article)
    assert assigns(:article).valid?
  end

  test "should get edit" do
    login_as(:eugene)
    get :edit, :id => @article.to_param
    assert_response :success
  end

  test "should update article" do
    login_as(:eugene)
    **put :update, :id => @article.to_param, :article => { :title => 'New Title' }**
    assert_redirected_to article_path(assigns(:article))
end

  test "should destroy article" do
    login_as(:eugene)
    assert_nothing_raised { Article.find(@article.to_param)}

    assert_difference('Article.count', -1) do
      delete :destroy, :id => @article.to_param
    end
    assert_response :redirect
    assert_redirected_to articles_path

    assert_raise(ActiveRecord::RecordNotFound)  { Article.find(@article.to_param) }
  end
end

I'm running Rails 4.1.10, and I'm pretty sure that my error has something to do with the Strong Params gem that Rails uses now. If someone could show me the problem with my code and explain why it's wrong that would be greatly appreciated.

This is the actual article_controller file, line 50 and line 67 are respectively outlined in stars:

class ArticlesController < ApplicationController   
  before_filter :authenticate, :except => [:index, :show]

  def index
    @articles = Article.all

    respond_to do |format|
      format.html
      format.xml  { render :xml => @articles }
    end   end
     def show
    @article = Article.find(params[:id])

    respond_to do |format|
      format.html 
      format.xml  { render :xml => @article }
    end
  end

  def new
    @article = Article.new

    respond_to do |format|
      format.html 
      format.xml  { render :xml => @article }
    end
  end

  def edit
    @article = current_user.articles.find(params[:id])
  end

  def create
    @article = current_user.articles.new(article_params)

    respond_to do |format|
      if @article.save
        format.html { redirect_to(@article, :notice => 'Article was successfully created.') }
        **format.xml  { render :xml => @article, :status => :created, :location => @article }**
      else
        format.html { render :action => "new" }
        format.xml  { render :xml => @article.errors, :status => :unprocessable_entity }
      end
    end
  end

  def notify_friend
    @article = Article.find(params[:id])
    Notifier.email_friend(@article, params[:name], params[:email]).deliver
    redirect_to @article, :notice => "The message has been sent to your friend" 
  end

  def update
    **@article = current_user.articles.find(article_params)**

    respond_to do |format|
      if @article.update_attributes(params[:article])
        format.html { redirect_to(@article, :notice => 'Article was successfully updated.') }
        format.xml  { head :ok }
      else
        format.html { render :action => "edit" }
        format.xml  { render :xml => @article.errors, :status => :unprocessable_entity }
      end
    end   
  end

  def destroy
    @article = current_user.articles.find(params[:id])
    @article.destroy

    respond_to do |format|
      format.html { redirect_to(articles_url) }
      format.xml  { head :ok }
    end   
  end 

end

def article_params
  params.require(:article).permit(:title, :location, :categories, :excerpt, :body, :published_at)
end