<%= stylesheet_link_tag    'application', media: 'all', 'data-turbolinks-track' => true %>
  <%= javascript_include_tag 'application', 'data-turbolinks-track' => true %>

require 'test_helper'

class CategoryTest < ActiveSupport::TestCase

  def setup
    @category = Category.new(name: "sports")
  end


  test "category should be valid" do
    assert @category.valid?
  end

  test "name should be present" do
    @category.name = " "
    assert_not @category.valid?
  end

  test "name should be unique" do
    @category.save
    category2 = Category.new(name: "sports")
    assert_not category2.valid?
  end

  test "name should not be too long" do
    @category.name = "a" * 26
    assert_not @category.valid?
  end

  test "name should not be too short" do
    @category.name = "aa"
    assert_not @category.valid?
  end


end

1) Error:
CategoriesControllerTest#test_should_get_show:
ActionView::Template::Error: undefined method `[]' for nil:NilClass
    app/views/layouts/application.html.erb:5:in `_app_views_layouts_application_html_erb__1500379652327484675_33850180'
    test/controllers/categories_controller_test.rb:20:in `block in <class:CategoriesControllerTest>'

  2) Error:
CategoriesControllerTest#test_should_get_categories_index:
ActionView::Template::Error: undefined method `[]' for nil:NilClass
    app/views/layouts/application.html.erb:5:in `_app_views_layouts_application_html_erb__1500379652327484675_33850180'
    test/controllers/categories_controller_test.rb:10:in `block in <class:CategoriesControllerTest>'

  3) Error:
CategoriesControllerTest#test_should_get_new:
ActionView::Template::Error: undefined method `[]' for nil:NilClass
    app/views/layouts/application.html.erb:5:in `_app_views_layouts_application_html_erb__1500379652327484675_33850180'
    test/controllers/categories_controller_test.rb:15:in `block in <class:CategoriesControllerTest>'