As a test team, we generally do the best we can with what we have, and what we have never exactly matches production....
What we test on and how the software is configured does not match -- cannot match -- every configuration possibility a customer encounters. What a staging environment provides is an exact replica of production for testing efforts. The hardware, servers, platforms, databases, database triggers and anything else match exactly to your production environment.
It goes without saying that neither a company, nor a test team, nor any development organization can guarantee their software is defect-free. I can guarantee you that there is never enough time to cover all test scenarios to ensure code is defect-free, whether using automated or manual test efforts. Therefore, as testers, we have to use risk analysis to determine what areas are more problematic and require more focused testing. Validating that risk analysis requires information about the way the application runs in the actual production environment.
What is a staging environment?
A stage or staging environment is an environment for testing that exactly resembles the production environment. In other words, it's a complete but independent copy of the production environment, including the database. Staging provides a true basis for QA testing because it precisely reproduces what is in production. A well-implemented staging environment makes it possible to define the important standards and test those accurately.
Now, consider a test team that executes all of their tests in a nonproduction environment. For example, in most software development organizations, there are multiple environments for development coding and QA testing on the way to a production release. However, neither the development nor the QA test environment has exactly what the production environment does.
The database is usually not the same -- close perhaps, but not the same. The configurations and platforms may be different. The back-end third-party systems used may differ due to the cost of licensing or installation restrictions. The bottom line is that what they're testing is not exactly the production code because they're testing on nonproduction environment with simulated data. They face the distinct possibility of releasing critical defects to customers because they're not testing in a real-world environment.
Developers and QA pros tweak these environments as needed to simulate testing on production, but simulate does not mean create the same thing. The test team won't see the issues when the environment is not the same because the playing field, so to speak, is not even. Sounds like a place for test escapes and defects to thrive and grow. Maybe there's a better way.
Why is a staging environment critical?
Testing on a staging environment provides a more accurate measure of performance capacity and functional correctness. As Web applications become more mission-critical for customers, it becomes increasingly important to test on environments that exactly mimic production because it's production where customers use your application. Any defect found in production is a miss or an escape. Any defects experienced by customers in production negatively impacts your application's and company's reputation.
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In the current business climate, as new applications become more widely available in health care, government infrastructure and financial transactions, it's become more critical that your application doesn't fail. It's critical to not offend, disappoint or annoy your customer base, because with so many products and producers, it's much easier for costumers-- even internal customers -- to switch.
Customers prefer not to be surprised. No one wants their system to go down or to go really, really, really slowly. As workers, we don't want to be negatively impacted at all by software upgrades. As working professionals, we want software upgrades to be seamless, unnoticeable -- a non-event. The only way to truly ensure that your software doesn't interrupt or interfere with your professional users is to test on a staging environment.
As a company, it's tempting to bypass creating a staging environment for preproduction testing. However, when producing mission-critical software of any kind, the staging environment is imperative to ongoing success.