Why We Can’t Test Everything

Many people perceive testing as a process of testing every possible case to ensure that a product performs perfectly at all times. This was also my perspective on good testing at the start of my manual QA career. As I progressed through my work and became more experienced in this field, I realized that this type of testing is unrealistic.

The biggest challenge in testing isn’t how much we test — it’s determining how wisely we will select what we test.

The issue begins with the complexity of software products. In today’s applications, there are numerous features, configuration options, user roles, and environments. A minor modification in one area of the product could have an unpredictable effect on a completely different area of the product. With the sheer number of test cases possible for each feature, if we attempted to test every possible combination of input, state, and user behavior; the number of test cases becomes infinite. It is not feasible to cover all potential test cases due to limited time, budget, and human resource availability.

Exhaustive testing is a testing technique in which the tester attempts to test every functionality of a product using every possible combination. Exhaustive testing is not feasible with modern software. When testing even a single feature such as the ability to create a new user account in a product, there are dozens, or even hundreds, of combinations. When looking at a complete product with a payment component, user profile management, integration with external products/systems, and security requirements, exhaustive testing would be virtually impossible to achieve within a reasonable amount of time.

That is why it’s very important to test effectively, not exhaustively.

To effectively test software QA Engineers are using different testing techniques.

The easiest and most used testing technique is “Risk-Based Testing.” Instead of treating all features equally, we analyze risks and concentrate our efforts where failures would cause the most damage – financial loss, security issues, or poor user experience. To use this technique, you should analyze Impact (how serious the consequences of a failure are) and Probability (how likely a failure is to occur). For example, the payment process has a much higher priority than a rarely used settings page. Even small bugs in critical areas deserve more attention.

Next commonly used technique is “Equivalence Partitioning”. Instead of testing every possible input, we group inputs into classes that should behave similarly. If one value from a group works correctly, there is a high chance others will too. This significantly reduces the number of test cases while maintaining reasonable coverage.

“Boundary Value Analysis” technique is also commonly used when testing software because many bugs may appear at boundaries. It’s very important to focus on minimum and maximum values, empty fields, and edge cases. This approach often reveals defects that normal scenarios do not.

More experienced testers might want to use “Exploratory Testing” because not everything can or should be scripted. Exploratory testing allows us to use intuition, experience, and curiosity. While exploring the system, we often discover unexpected behavior that no predefined test case could predict.

After trying different techniques, you can start combining them into a single, balanced testing strategy.

The implementation usually follows these steps: understand the product and business goals; identify high-risk areas; select appropriate testing techniques; adapt to constraints.

By combining and applying different approaches, the quality of testing will be significantly improved. You will be able to find more critical bugs earlier, testing will become more structured, and communication with the team will be clearer. 

Accepting that perfection is impossible allows us to focus on realistic goals and continuous improvement rather than chasing unattainable completeness.

At Swan Software Solutions, our team of QA engineers keeps software running well. To discover more about how our team could help your team with testing or a custom solution, contact us.