Add basic coverage for `AfterUnallowDomainService` class (#29324)

spec/services/after_unallow_domain_service_spec.rb

@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe AfterUnallowDomainService do
+  describe '#call' do
+    context 'with accounts for a domain' do
+      let!(:account) { Fabricate(:account, domain: 'host.example') }
+      let!(:test_account) { Fabricate(:account, domain: 'test.example') }
+      let(:service_double) { instance_double(DeleteAccountService, call: true) }
+
+      before { allow(DeleteAccountService).to receive(:new).and_return(service_double) }
+
+      it 'calls the delete service for accounts from the relevant domain' do
+        subject.call 'test.example'
+
+        expect(service_double)
+          .to_not have_received(:call).with(account, reserve_username: false)
+        expect(service_double)
+          .to have_received(:call).with(test_account, reserve_username: false)
+      end
+    end
+  end
+end