DEV: Add system spec for categories page (#29621)

Follow up to commit 948e283e0f0654a7bd1d48554623afc84beb03f4.

spec/system/discovery_category_spec.rb

@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+
+describe "Discovery Category Routes", type: :system do
+  fab!(:category) do
+    Fabricate(:category, show_subcategory_list: true, subcategory_list_style: "boxes")
+  end
+
+  fab!(:subcategory1) { Fabricate(:category, parent_category: category) }
+  fab!(:subcategory2) { Fabricate(:category, parent_category: category) }
+  fab!(:subcategory3) { Fabricate(:category, parent_category: category) }
+
+  let(:discovery) { PageObjects::Pages::Discovery.new }
+
+  it "uses desktop_category_page style on categories and subcategories page" do
+    visit "/categories"
+    expect(page).to have_css(".category-list")
+
+    visit "/c/#{category.slug}/subcategories"
+    expect(page).to have_css(".category-list")
+  end
+
+  it "uses subcategory_list_style on category page" do
+    visit "/c/#{category.slug}"
+    expect(page).to have_css(".category-boxes")
+
+    visit "/c/#{category.slug}/all"
+    expect(page).to have_css(".category-boxes")
+
+    visit "/c/#{category.slug}/none"
+    expect(page).to have_css(".category-boxes")
+  end
+end