Add tests for browse controller
user
```ruby
require_relative "../test_helper"

class BrowseControllerTest < ActionController::TestCase
  context "GET index" do
    should "list all categories" do
      content_api_has_root_sections(["crime-and-justice"])
      get :index
      url = "http://www.test.gov.uk/browse/crime-and-justice"
      assert_select "ul h2 a", "Crime and justice"
      assert_select "ul h2 a[href=#{url}]"
    end
  end

  context "GET section" do
    should "list the sub sections" do
      content_api_has_section("crime-and-justice")
      content_api_has_subsections("crime-and-justice", ["alpha"])
      get :section, section: "crime-and-justice"

      assert_select "h1", "Crime and justice"
      assert_select "ul h2 a", "Alpha"
    end

    should_eventually "404 if the section does not exist"
  end

  context "GET sub_section" do
    should "list the content in the sub section" do
      content_api_has_section("crime-and-justice/judges", "crime-and-justice")
      content_api_has_artefacts_in_a_section("crime-and-justice/judges", ["judge-dredd"])

      get :sub_section, section: "crime-and-justice", sub_section: "judges"

      assert_select "h1", "Crime and justice"
      assert_select "h2", "Judges"
      assert_select "li h2 a", "Judge dredd"
    end

    should_eventually "404 if the sub section does not exist"
  end
end
```
assistant