Day 5
Handle your first error
Turn an error into reproducible facts. Record the behavior and full error, locate the smallest cause, then repeat the same path after the fix.
- Suggested time
- 50-70 minutes
- Completion evidence
- Error card, fix, and retest
Choose one real failure
Use a failed item from Day 4. Do not damage a real project on purpose just to create practice.
Separate observation from theory
"The button does nothing" is an observation. "The event listener is wrong" is a hypothesis. Preserve what you can see before asking for a cause.
ReproduceRepeat the shortest path from a normal start.
RecordSave the behavior, full error, and recent change.
LocateBind each cause claim to a file or error.
RetestRepeat the original path and related checks.
Diagnose before editing
Failure diagnosis
Diagnose first. Do not modify files or install dependencies.
Project: personal maker page
Expected behavior: clicking "View my 16th case" displays "My first release goal: invite one real user to try it."
Actual behavior: [paste what you observed]
Shortest reproduction steps: [write them]
Full error text: [paste exactly, or write "No visible error"]
Most recent change: [what changed]
Return:
1. Facts confirmed by files and errors.
2. The most likely cause with file or error evidence.
3. What is still uncertain.
4. The smallest fix plan for this failure only.
5. The tests that must be repeated after the fix.
Do not refactor. Wait for approval.Approve the fix only when
- The cause points to a real file and location.
- The plan handles only the current failure.
- The original path will be repeated after the fix.
Apply the smallest fix and retest
Approve the fix
I approve the smallest fix plan. Apply only that fix.
1. Change only the files and locations in the plan.
2. Add no feature and do not restyle or rewrite the page.
3. Repeat the original reproduction path.
4. Retest related existing behavior.
5. Report the actual change, test action, observed result, and anything still unverified.
If the real files differ from the plan, stop and explain the difference.Error card, fix, and retest
A useful error card lets another person reproduce the problem and understand why only this location changed.
See the remaining course path