The refactoring safety net
Your black box tests will give you the confidence and keep you safe
Don’t underestimate the value of keeping your unit tests in shape. When it’s time to refactor, you can use your black box tests to complete the job faster. The refactoring safety net.
Unit test
There are many good reasons to unit test your code. One important reason is their role as a safety net. When done correctly, unit tests protect your code during refactoring. Since developers rarely write the ideal solution on the first try, they need to refactor constantly. But to take advantage of your tests when refactoring, your design must allow changing the implementation without rewriting your tests.
Black box tests will help you during the process by testing functionality without focusing on implementation details. White box tests, which rely on internal structures, increase risk and make the process more difficult. Changing more code than necessary is something no developer enjoys.
The less your tests know about the internal implementation of your components, the more useful they will be during refactoring. If you frequently change your unit tests alongside the code, they lose their ability to verify consistent behavior and quality.
Enforce a good design
When you develop a new component, tests help you enforce good design. Some developers dislike writing tests and make excuses. They may claim testing is too difficult or even impossible. Well, if it’s difficult to test, it’s probably difficult to use. The design might need adjustments. Perhaps the business logic is misplaced, or a static dependency exists where it shouldn’t.
Coding against interfaces simplifies testing significantly. Clear dependencies and loose coupling between components make mocking much easier. Try to separate different concerns, avoid mixing code for transaction management and database access with your business rules. Usually, this also makes it easier to put the right code in the right place.
Getting inside the box
Feeling compelled to test a private method or access private fields may signal issues in your class design. The class might have unclear dependencies, be overly coupled, or handle too many responsibilities.
Examine the design carefully before introducing test frameworks that break encapsulation. Reserve such frameworks for situations with no alternatives. Use them only when verifying implementation details is absolutely necessary. In a well-designed system, unit tests protect the interface and functionality of each component. This protection makes refactoring much faster. Black box tests will provide confidence and ensure safety during the process.
Mattias Olofsson
Mattias is a software developer with project management experience. He is a quick learner with excellent analytical, design and problem solving skills. He has long experience from design and development of technically challenging systems. He has also been involved in team and technical project management as well as architecture work. He is comfortable working independently or as part of a team and always strives to perform his best and deliver on time and in full.
