Defect Clustering

What is Defect Clustering?

Defect clustering is the observation that a small number of modules or components in an application tend to contain the majority of defects, following the Pareto principle (roughly 80% of defects are found in 20% of modules).

Why Defect Clustering Happens

• Certain modules are more complex and thus more error-prone.
• Modules developed under tight deadlines may receive less careful implementation.
• Areas with frequent changes are more likely to introduce new defects.

Why It Matters for Testing

Recognising defect clustering supports risk-based testing — modules with a history of defects should receive more thorough and repeated testing attention in future test cycles.