Heuristics: Generating Solutions Quickly adjective: “serving to discover.” noun: “a useful method that doesn’t always work.” “Heuristic reasoning is not regarded as final and strict but as provisional and plausible only, whose purpose is to discover the solution to the present problem.” - George Polya, How to Solve It

Some Everyday Heuristics It’s dangerous to drink and drive. A bird in hand is worth two in the bush. Nothing ventured, nothing gained. Sometimes people stash their passwords near their computers. Try looking there. Stores are open later during the Holidays. If your computer is behaving strangely, try rebooting. If it’s very strange, reinstall Windows. If it’s a genuinely important task, your boss will follow-up, otherwise, you can ignore it.

How Heuristics Differ from Other Procedures or Methods Heuristics are known to be wrong, at least some of the time. No one can say for sure when a heuristic will work. Heuristics aid or focus an open-ended problem-solving or solution-searching effort. Heuristics can substitute for complete or rigorous analysis.

Tunnel-Vision is Our Great Occupational Hazard invisible problems Problems you can find with your biases… invisible problems

A Tester’s Attitude Cautious Curious Critical (and Courageous) Jump to conjectures, not conclusions. Practice admitting “I don’t know.” Have someone check your work. Curious What would happen if…? How does that work? Why did that happen? Critical Proceed by conjecture and refutation. Actively seek counter-evidence. Good testers are hard to fool. (and Courageous)

Important Vocabulary Abductive inference is a way to make respected guesses. Conjectures (a.k.a. hypotheses) help us remember that we may be wrong about our beliefs. Refutation means checking how you could be wrong, before trusting a conjecture. Evidence is either consistent with (corroborates) or inconsistent with a given conjecture. Heuristics help us get the right ideas at the right times. Raising questions and issues is the heart of testing.

The Triangle Program This program takes three numbers as input. The numbers represent the dimensions of a triangle. When you click on the check button, the program tells you what kind of triangle the sides represent: scalene (no side equal to any other) isosceles (two sides are equal) equilateral (all sides are equal) I want you to test this program. Any questions?