Error Guessing
Error guessing relies on a tester's experience and intuition to predict where defects are likely to hide — based on patterns from past bugs, common developer mistakes, and areas of known complexity — rather than following a formal, systematic technique.
It's less a defined method than a skill built from experience: testers who've seen enough bugs develop a sense for where they tend to cluster — boundary conditions, error handling paths, recently-changed code, areas with complex conditional logic — and target those areas first.
Error guessing works best as a complement to systematic techniques, not a replacement for them — it catches things a formal technique might miss precisely because it isn't constrained by a predefined structure, but it's inherently less repeatable and more dependent on who's doing the testing.
