The Main Principles of Software Testing
Testing shows presence of
mistakes. Testing is aimed at detecting the defects within a piece of
software. But no matter how thoroughly the product is tested, we can never be
100 percent sure that there are no defects. We can only use testing to reduce
the number of unfound issues.
Exhaustive testing is
impossible. There is no way to test all combinations of data inputs,
scenarios, and preconditions within an application. For example, if a single
app screen contains 10 input fields with 3 possible value options each, this
means to cover all possible combinations, test engineers would need to create
59,049 (310) test scenarios. And what if the app contains 50+ of such screens?
In order not to spend weeks creating millions of such less possible scenarios,
it is better to focus on potentially more significant ones.
Early testing. As mentioned
above, the cost of an error grows exponentially throughout the stages of the
SDLC. Therefore, it is important to start testing the software as soon as
possible so that the detected issues are resolved and do not snowball.
Defect clustering. This
principle is often referred to as an application of the Pareto principle to
software testing. This means that approximately 80 percent of all errors are
usually found in only 20 percent of the system modules. Therefore, if a defect
is found in a particular module of a software program, the chances are there
might be other defects. That is why it makes sense to test that area of the
product thoroughly.
Pesticide paradox. Running
the same set of tests again and again won’t help you find more issues. As soon
as the detected errors are fixed, these test scenarios become useless.
Therefore, it is important to review and update the tests regularly in order to
adapt and potentially find more errors.
Testing is context dependent.
Depending on their purpose or industry, different applications should be tested
differently. While safety could be of primary importance for a fintech product,
it is less important for a corporate website. The latter, in its turn, puts an
emphasis on usability and speed.
Absence-of-errors fallacy.
The complete absence of errors in your product does not necessarily mean its
success. No matter how much time you have spent polishing your code or
improving the functionality if your product is not useful or does not meet the
user expectations it won’t be adopted by the target audience.
While the above-listed principles are undisputed guidelines for every software testing professional, there are more aspects to consider. Some sources note other principles in addition to the basic ones:
- Testing must be an independent process handled by unbiased professionals.
- Test for invalid and unexpected input values as well as valid and expected ones.
- Testing should be performed only on a static piece of software (no changes should be made in the process of testing).
- Use exhaustive and comprehensive documentation to define the expected test results.