Example usage
A tester with experience in payment systems suspects that a discount code field may accept an overly long string or a negative quantity. Instead of deriving cases from the specification, they design tests specifically to provoke those suspected defects: a 500-character code, a negative quantity, a code containing special characters. This is error guessing — using the tester’s experience to anticipate what defects might be present and to design tests to expose them.
FAQ
Is error guessing a black-box or white-box technique? It is an experience-based test design technique. The official definition describes it as a test design technique where the tester’s experience is used to anticipate defects — it does not rely on analyzing code internals (white-box) nor exclusively on the specification (black-box), but on the tester’s knowledge of typical mistakes.
Why is error guessing called “experience-based”? Because its power comes from the tester’s experience with similar systems, typical programming mistakes, and past defects. A fresh tester will guess fewer and weaker cases.
Can error guessing be documented? Yes. Teams capture their experience in checklists of common mistakes, defect catalogs, and lessons learned, turning tacit knowledge into reusable test ideas.
Does error guessing replace other techniques? No. It complements them — experience-based techniques are often combined with specification-based and structure-based techniques to broaden coverage.
Is exploratory testing the same as error guessing? No. Exploratory testing is an experience-based approach where tests are simultaneously designed, executed, and adapted based on learning; error guessing is a specific technique for anticipating defects. Error guessing often feeds exploratory testing sessions.
Related terms
- experience-based testing — the family of techniques error guessing belongs to
- exploratory testing — simultaneous design and execution with adaptation
- test charter — the mission that guides experience-based sessions
- defect — what error guessing tries to anticipate
- error — the human action behind a defect
- test design technique — the wider family of test derivation methods
