Software testing has long been a critical component of ensuring software quality. If you are familiar with the ACCELERATE book, you'll know that continuous delivery is key to achieving a high-performance organization, and a good testing strategy is essential to enable it.

There are many resources about testing, integration tests, unit tests, TDD, and so on. I would like to have a more abstract discussion about what you should to consider before taking decisions on testing.

Long story short, after several meaningful discussions with many teams, I've noticed that we always end up with four key principles, which I describe using the acronym W.O.R.D.

W.O.R.D.

• It Works.
• It Orients the development and code design.
• It is easy to Refactor.
• It is a Debugging tool.

It WORKS!

One of the main concerns in software quality is to:

"satisfy the customer through early and continuous delivery of valuable software". Agile Manifesto

Any testing strategy must provide the safety that any change that passes all tests can be ship to production with no fear. A testing strategy that covers the application into different levels is required to reach that confidence.

It also requires a team that fully understands that software quality is a role of all. Testing culture is an important matter here and Developers should not write tests just to reach a quality gate metric.

It ORIENTS the development and code design!

A good testing strategy should make the development process easier by allowing you to test small parts of a complex solution individually.

Also, tests can provide valuable insights into the quality of your code. If the test is too complex to read and cannot be simplified, it may indicate a code smell not in the test itself but in the production code.

It is easy to REFACTOR!

I often hear people complaining about how tests make their life miserable during the refactoring process. Tests are not supposed to break during a refactor. If it does, it is a smell that your tests are not focusing on at the crucial point of any application: Its behavior.

Developers sometimes focus too much on implementation details. If tests are too tightly coupled to the implementation, refactoring can be difficult and time-consuming. It's important to strike a balance between testing implementation details and testing the application's behavior. Avoid relying too heavily on mocks and instead, focus on validating the behavior of the application.

It is a DEBUGGING tool

No application is completely bulletproof, and bugs will inevitably occur. When they do, your testing strategy must be capable of simulating these issues. If you're unable to replicate a bug, it suggests that there are certain scenarios that your test strategy isn't covering, which directly impacts the "It Works" principle.

Ensure that your testing strategy adapts to your application's increasing complexity.

With these four principles in mind, it's important to iterate and constantly evaluate your testing strategy with your team. Ensure that you are covering all four principles and look for ways to improve your testing approach. These simple principles can help you make better and more informed decisions about your testing strategy.