When we write code, we always want to believe that it works perfectly. But the reality is much harsher: bugs appear where you least expect them. That's why testing is an integral part of development. Let's figure out what types of testing there are and why they are needed.
Functional testing
This is a check of that the program does what it is supposed to do. For example, in an online store, functional testing will check:
whether the product is added to the cart,
whether the "Place an order" button works,
whether a purchase notification is received.
Non-functional testing
Answers the question: "how well does the application work?". Checks:
user-friendly interface,
page loading speed,
data security.
Unit testing
Checking individual functions of the program. For example, the discount calculation function is tested with different input data to make sure the result is correct.
Integration testing
Here, the interaction of the system parts is checked: the payment service and the shopping cart, the data exchange between the frontend and the backend.
System testing
This is already testing the entire system. The product is tested as if it were being used by a real user.
Load testing
What happens if thousands of users visit the site at the same time? Checks:
how many requests the server can handle,
at what load do errors begin,
where the bottlenecks of the system are.
Regression testing
Each new update can break the old functionality. Regression testing verifies that new changes do not introduce unexpected bugs.
Automated and manual testing 🤖 vs 🙋♂️
Manual — the tester checks the functionality himself. Flexible, but long.
Automated — tests are run by scripts. Fast, but requires customization.
Results
Testing is not just about finding bugs. It is a way to make sure that the product works correctly, is stable, and can withstand the load. The earlier you start testing, the cheaper the errors are.
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