From https://once.com/writebook

test/controllers/books/bookmarks_controller_test.rb

@@ -0,0 +1,33 @@
+require "test_helper"
+
+class Books::BookmarksControllerTest < ActionDispatch::IntegrationTest
+  setup do
+    sign_in :kevin
+  end
+
+  test "show includes a link to read the last read leaf" do
+    cookies["reading_progress_#{books(:handbook).id}"] = "#{leaves(:welcome_page).id}/3"
+
+    get book_bookmark_url(books(:handbook))
+
+    assert_response :success
+    assert_select "a", /Resume reading/
+  end
+
+  test "show includes a link to start reading if the last read leaf has been trashed" do
+    leaves(:welcome_page).trashed!
+    cookies["reading_progress_#{books(:handbook).id}"] = "#{leaves(:welcome_page).id}/3"
+
+    get book_bookmark_url(books(:handbook))
+
+    assert_response :success
+    assert_select "a", /Start reading/
+  end
+
+  test "show includes a link to start reading if no reading progress has been recorded" do
+    get book_bookmark_url(books(:handbook))
+
+    assert_response :success
+    assert_select "a", /Start reading/
+  end
+end