Debug Like a Scientist

Guessing is not a method

Sooner or later a bug arrives that no test predicted. Beginners debug by vibes: change something, run, change something else, run, until the error goes away and nobody knows why. That wastes hours and often buries the bug instead of fixing it.

Professionals run a hypothesis loop, the scientific method pointed at code:

1. Observe the symptom precisely. Not "it's broken" but "total is 6 when 5.0 was expected, for even-length input"
2. Hypothesize one specific cause: "the median picks the wrong index when the list length is even"
3. Predict something checkable: "then median([1, 2]) should return 2, not 1.5"
4. Experiment: run exactly that check
5. Confirmed? Fix it, and add the regression test from lesson 4-3. Refuted? Back to step 2 with what you learned

One rule makes the loop honest: change one thing per experiment. Change two and you cannot tell which one mattered.