From https://once.com/writebook

test/models/user_test.rb

@@ -0,0 +1,20 @@
+require "test_helper"
+
+class UserTest < ActiveSupport::TestCase
+  test "user does not prevent very long passwords" do
+    users(:david).update(password: "secret" * 50)
+    assert users(:david).valid?
+  end
+
+  test "new users get access to everyone books" do
+    everyone_book = Book.create!(title: "My new book", everyone_access: true)
+    other_book = Book.create!(title: "My secret book", everyone_access: false)
+
+    bob = User.create!(email_address: "bob@example.com", name: "Bob", password: "secret123456")
+
+    assert everyone_book.accessable?(user: bob)
+    assert_not everyone_book.editable?(user: bob)
+
+    assert_not other_book.accessable?(user: bob)
+  end
+end