Hi,
Before this line we need to reset the `Base.mode` for this [build](https://travis-ci.org/Shopify/active_merchant/jobs/11682809)

~~~ diff
+    ActiveMerchant::Billing::Base.mode = :production
+    assert_equal false, @paybox_system.test?
+    ActiveMerchant::Billing::Base.mode = :test
     assert @paybox_system.test?
~~~