While it is always a good idea to thoroughly test before adding our changes to the production system, sometimes, we can safely do our testing inside the production environment. If the modifications consist of functions that do not change any data and can be tested without affecting any ongoing production activity, it may be feasible to test within the production system.
Examples of modifications that may be able to be tested in the live production system can range from a simple inquiry page, a new analysis report, or when exporting data that is to be processed outside the system to a completely new subsystem that does not change any existing data. There are also situations where the only changes to the existing system are the addition of fields to existing tables. In such a case, we may be able to test just a part of the modification outside production, and then implement the table changes to complete the rest of the testing in the context of the production system...