Improve tests

#694

test/integration/api/domain_transfers_test.rb

@@ -46,6 +46,9 @@ class APIDomainTransfersTest < ActionDispatch::IntegrationTest
     assert_difference -> { @old_registrar.messages.count } do
       post '/repp/v1/domain_transfers', request_params, { 'HTTP_AUTHORIZATION' => http_auth_key }
     end
+
+    message = 'Domain transfer was approved, associated contacts were: ["jane-001", "william-001"] and registrant was john-001'
+    assert_equal message, @old_registrar.messages.last.body
   end
 
   def test_duplicates_registrant_admin_and_tech_contacts