how_to_debug.md

How to debug

1. Replicate the bug (multiple times). Investigate: When does it happen? Describe the bug:
   • When I do X
   • Y happens
   • But I expected (wanted) Z to happen
2. Form a hypothesis or educated guess about WHY the bug is happening
   • Read any errors, carefully — use debugging tools to fully understand what the error is telling you
   • Use your past experience with similar bugs to come up with ideas
3. Pick the most likely hypothesis
   • If you have a reason, a gut feeling, or a favorite, use those to guide you (those factors are listed roughly in order of how well you can rely on them to guide you)
4. Test a hypothesis
   • Use debugging tools to investigate the values of variables, arguments, and return values, the order your code executes in, and how often each piece runs
   • As you go, think through what you expect the results of each test to be. When the results of your testing don't match your expectations, that's a sign that you're getting closer to the source of the bug.
   • If your hypothesis is supported by the results of the tests, continue to 5
   • If not, try a different hypothesis (or make a new one) until you find a way to explain what's happening
5. ONLY only once you have a tested and supported hypothesis, try a fix based on that hypothesis
   • If it worked, rejoice!
   • If it didn't, remove your attempted fix, and go back to step 3 (or 2)