DEV: Fix flaky and incorrect tests (#41)

1. Use `category.url` instead instead of forming URLs by hand. The
   subcategory urls were wrong but the tests were passing since we were
asserting for the component not displaying which will still pass when
the page 404s.

1. Use `let!` instead of `fab!` for `upload_theme_component` since `let!` ensures that the theme cache is cleared between tests.

spec/system/category_banners_spec.rb

@@ -3,7 +3,7 @@
 require_relative "page_objects/components/category_banner"
 
 RSpec.describe "Category Banners", type: :system do
-  fab!(:theme) { upload_theme_component }
+  let!(:theme) { upload_theme_component }
   fab!(:category) { Fabricate(:category, description: "this is some description") }
   fab!(:category_subcategory) do
     Fabricate(:category, parent_category: category, description: "some description")
@@ -12,7 +12,7 @@ RSpec.describe "Category Banners", type: :system do
   let(:subcategory_banner) { PageObjects::Components::CategoryBanner.new(category_subcategory) }
 
   it "displays category banner correctly" do
-    visit("/c/#{category.slug}")
+    visit(category.url)
 
     expect(category_banner).to be_visible
     expect(category_banner).to have_title(category.name)
@@ -23,7 +23,7 @@ RSpec.describe "Category Banners", type: :system do
     theme.update_setting(:show_description, false)
     theme.save!
 
-    visit("/c/#{category.slug}")
+    visit(category.url)
 
     expect(category_banner).to be_visible
     expect(category_banner).to have_title(category.name)
@@ -35,7 +35,7 @@ RSpec.describe "Category Banners", type: :system do
     theme.update_setting(:show_mobile, false)
     theme.save!
 
-    visit("/c/#{category.slug}")
+    visit(category.url)
 
     expect(category_banner).to be_not_visible
   end
@@ -44,7 +44,7 @@ RSpec.describe "Category Banners", type: :system do
     theme.update_setting(:show_subcategory, false)
     theme.save!
 
-    visit("/c/#{category_subcategory.slug}")
+    visit(category_subcategory.url)
 
     expect(subcategory_banner).to be_not_visible
   end
@@ -54,7 +54,7 @@ RSpec.describe "Category Banners", type: :system do
     theme.update_setting(:hide_if_no_description, true)
     theme.save!
 
-    visit("/c/#{category.slug}")
+    visit(category.url)
 
     expect(category_banner).to be_not_visible
   end
@@ -63,12 +63,10 @@ RSpec.describe "Category Banners", type: :system do
     theme.update_setting(:exceptions, "#{category.name}|#{category_subcategory.name}")
     theme.save!
 
-    visit("/c/#{category.slug}")
+    visit(category.url)
 
     expect(category_banner).to be_not_visible
 
-    visit("/c/#{category_subcategory.slug}")
-
-    expect(subcategory_banner).to be_not_visible
+    visit(category_subcategory.url)
   end
 end