Defects tend to cluster in some areas of the software under test. It may happen due to higher complexity, algorithms, or a higher number of integrations in a few constrained segments of the software.

These defect clusters can be tricky, both to find and to deal with. Testers need to be on constant alert for ways to isolate defect clusters and devise ways to overcome them, fight those defects and move on to new clusters.

In my article for Gurock blog, I discussed some ways to fight Defect Clusters in Software Testing:

Locating Defect Clusters

Most defects tend to cluster in certain areas of your software. It is one of the seven testing principles. Many testers intuitively know of these defect-prone areas, but we can still strive to be on the lookout for clusters of defects in a number of ways, like utilizing

Metrics

Using metrics like defect density charts or module-wise defect counts, we can examine the history of defects that have been found and look for areas, modules, or features with higher defect density. This is where we should begin our search for defect clusters. Spending more time testing these areas may lead us to more defects or more complex use cases to try out.

For example, the chart below shows that Module 4 has the most defects, so it would be smart to continue concentrating on that module in the future.

History

Use the defect management system and the history of the software to go through older defects, and try to replicate them in the system. You will get to know the system’s history, where it broke and how it works now. You may learn a lot about the software and find many new areas to test.

Experience

A tester’s intuition, experience and history with the product is by far the best way to find defect clusters. Lessons learned by experienced teammates should be shared with new coworkers so that the knowledge can be passed on, utilized and improved upon by exercising these defect-prone areas with new perspectives.

Fighting Defect Clusters

Defect clustering follows the Pareto rule that 80% of the defects are caused by 20% of the modules in the software. It’s imperative for a tester to know which 20% of modules have the most defects so that the maximum amount of effort can be spent there. That way, even if you don’t have a lot of time to test, hopefully, you can still find the majority of defects.

Once you know the defect cluster areas, testers can focus on containing the defects in their product in a number of ways. Continue Reading—>