Q12 of 38 · Test design
Compare error guessing with experience-based testing.
Short answer
Short answer: Error guessing is a focused technique — the tester guesses likely failure points based on intuition or prior bugs and tests them specifically. Experience-based testing is the umbrella covering exploratory, checklist, and attack testing — any approach where the tester's experience drives test design rather than formal techniques.
Detail
The two terms overlap but aren't synonyms. Error guessing is one of several experience-based techniques; experience-based testing is the umbrella.
Error guessing is targeted. The tester reads the spec, looks at the code or screen, and asks "where would I be likely to have made a mistake if I were the developer?" Common targets: empty inputs, leading/trailing spaces, very long strings, special characters, zeros and negatives, null/undefined, off-by-one errors, time-zone bugs, leap years, race conditions, encoding issues.
Experience-based testing is the umbrella. It includes:
- Error guessing (above).
- Exploratory testing (charters, sessions, learn-as-you-go).
- Checklist-based testing (running through a personal or team-curated list — accessibility, security, mobile responsive, etc.).
- Attack testing (deliberate adversarial behaviour based on prior knowledge of common attack vectors).
When to lean on each:
- Error guessing is fast and targeted — useful when you have 30 minutes and want quick coverage of likely-failure points. Best paired with formal techniques (EP/BVA/decision tables) so it's not your only approach.
- Exploratory is for new or evolving features where you can't write tests in advance.
- Checklists are for ensuring you don't forget the cross-cutting concerns (a11y, security, perf) that no single test technique covers.
The signal: distinguishing formal techniques (EP, BVA, decision tables — they don't need experience to apply) from experience-based ones (which do). Strong testers blend both — formal for systematic coverage, experience-based for intuition-led depth.
The senior critique: experience-based testing is only as good as the team's collective experience. Junior teams under-cover error guessing because they don't yet have the pattern library; checklists help bootstrap that.