What should go on my test code? Unlike we think, it is a common question among the developers - main the newcomers - that advendure themselves in the world of programming. To start talking about this topic, some questions need to be answered and one of them is: "what are tests and why are they so important?". Tests are not only pieces of code responsible for ensuring a behavior in your main codebase, they tell you a story, they are responsible for teaching you things about your just-finished code that you did not even know.

But... Why does all these fine words mean? Basically, they tell you that tests are not exactly focused on ensuring behaviors that are already expected but the ones that we are not really expecting, and this is a really hard task that requires not only technical knowledge, but business knowledge about what you are doing. Tests are not meant to verify the basic, check database connections correctness or even validate classes and methods, their real and glorious objective is to ensure that - technically - your application mets all the requirements to be reliable to execute your business rules.

The main responsibility of a test is to track and ensure consistent behaviors that composes the pipeline to execute your business rules in a reliable way with meaningful causes and effects.

Meaningful causes and effects

Every effect will have a cause - and this does not change in the context of your application. Look at your final users as unpredictable sources of different causes that will end on different effects. Create your tests based on that concept, try to explore and select ways that your users have to possibly break your application. Also learn from past mistakes, creating tests that are responsible for trying to reproduce previous bugs and may fail.

Thinking on resilience and reliability

In the most basic meaning of the words that can fit for that context, we can identify "reliability" as the capability of your system to survive to expected causes such as power outages, denial of service attacks, cloud outages and environmental causes that usually happens time to time. But the main challenge of any development team is to ensure resilience - the capacity to handle unexpected problems - I mean - the capacity to handle problems like invasion attempts, unprompted system breaks and other random problem. This kind of capacity is not directly related to "how should I solve that problem automatically?" and more like to: "what should I do to avoid that compromised part breaking the rest of the system? how can I properly isolate my current problem and also gather sufficient information that will be sent to my logs to future troubleshoot?".

Conclusion

Testing can be tricky. Testing don't work only as a way to "see if something else is breaking", but a direct tool to act as a truth source during a project development. Tests are meant to be meaningful, to ensure resilience and make sure your project is following consistent patterns in order to attend your customers in the most profitable way.