Add specs for UrlValidator (#9699)

spec/validators/url_validator_spec.rb

+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe UrlValidator, type: :validator do
+  describe '#validate_each' do
+    before do
+      allow(validator).to receive(:compliant?).with(value) { compliant }
+      validator.validate_each(record, attribute, value)
+    end
+
+    let(:validator) { described_class.new(attributes: [attribute]) }
+    let(:record)    { double(errors: errors) }
+    let(:errors)    { double(add: nil) }
+    let(:value)     { '' }
+    let(:attribute) { :foo }
+
+    context 'unless compliant?' do
+      let(:compliant) { false }
+
+      it 'calls errors.add' do
+        expect(errors).to have_received(:add).with(attribute, I18n.t('applications.invalid_url'))
+      end
+    end
+
+    context 'if compliant?' do
+      let(:compliant) { true }
+
+      it 'not calls errors.add' do
+        expect(errors).not_to have_received(:add).with(attribute, any_args)
+      end
+    end
+  end
+end