Refer to constant values from api/v1/apps request spec (#33488)

spec/models/doorkeeper/application_spec.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe Doorkeeper::Application do
+  describe 'Associations' do
+    it { is_expected.to have_many(:created_users).class_name('User').inverse_of(:created_by_application).with_foreign_key(:created_by_application_id) }
+  end
+
+  describe 'Validations' do
+    it { is_expected.to validate_length_of(:name).is_at_most(described_class::APP_NAME_LIMIT) }
+    it { is_expected.to validate_length_of(:redirect_uri).is_at_most(described_class::APP_REDIRECT_URI_LIMIT) }
+    it { is_expected.to validate_length_of(:website).is_at_most(described_class::APP_WEBSITE_LIMIT) }
+  end
+end