Author: Haroon Khalil

cAs I said, I tend to favor unit testing. I appreciate the advantages that unit tests give me. They are easy to write, they are fast, I can write them intertwined with production code, and so on. I also believe that unit testing fits very well with the way software developers work. When developers implement…

With a clear understanding of the different test levels and their benefits, we have to decide whether to invest more in unit testing or system testing and determine which components should be tested via unit testing and which components should be tested via system testing. A wrong decision may have a considerable impact on the…

To get a more realistic view of the software and thus perform more realistic tests, we should run the entire software system with all its databases, frontend apps, and other components. When we test the system in its entirety, instead of testing small parts of the system in isolation, we are doing system testing (see…

Unit tests focus on the smallest parts of the system. However, testing components in isolation sometimes is not enough. This is especially true when the code under test goes beyond the system’s borders and uses other (often external) components. Integration testing is the test level we use to test the integration between our code and…

Whenever we talk about pragmatic testing, one of the first decisions we need to make is the level at which to test the code. By a test level, I mean the unit, integration, or system level. Let’s quickly look at each of them.

Finally, note that a software system that works flawlessly but is of no use to its users is not a good software system. “Coverage of code is easy to measure; coverage of requirements is another matter.” Software testers face this absence-of-errors fallacy when they focus solely on verification and not on validation. A popular saying that may help…

The context plays an important role in how we devise test cases. For example, devising test cases for a mobile app is very different from devising test cases for a web application or software used in a rocket. In other words, testing is context-dependent. Most of this book tries to be agnostic about context. The…

As Dijkstra used to say, “Program testing can be used to show the presence of bugs, but never to show their absence.” In other words, while we may find more bugs by simply testing more, our test suites, however large they may be, will never ensure that the software system is 100% bug-free. They will…

As I said earlier, given that exhaustive testing is impossible, software testers have to prioritize the tests they perform. When prioritizing test cases, note that bugs are not uniformly distributed. Empirically, our community has observed that some components present more bugs than others. For example, a Payment module may require more rigorous testing than a Marketing module. As a…

There is no silver bullet in software testing. In other words, there is no single testing technique that you can always apply to find all possible bugs. Different testing techniques help reveal different bugs. If you use only a single technique, you may find all the bugs you can with that technique and no more.…