Free guided interview rehearsal
Find the fix. Explain the why.
Work through three different debugging situations. After each, rehearse a short explanation of the evidence, your change and the check that proves it. Take one step per session at your own pace.
All three labs can be tried without signup. Sign in for account progress; guest workspaces expire after two hours. This is practice, not an interview score or a hiring guarantee.
Practise explaining the investigation
After each fix, spend two minutes explaining your reasoning aloud. Use these prompts for your own reflection.
- What failing behaviour did you reproduce?
- Which observation ruled out your first hypothesis?
- Why does your change address the cause?
- Which check would catch this regression?
Step 1 · Boundary reasoning
Pagination off by one
Complete the free lab, then come back and explain what changed.
Step 2 · Following data through an API
The Filter That Swallowed False
Complete the free lab, then come back and explain what changed.
Step 3 · Configuration diagnosis
Wrong Port, Right Service
Complete the free lab, then come back and explain what changed.
Notes stay on this browser and device. They are not synced to your account, submitted for grading or included in analytics.
Review the work behind your explanation
Pro adds private evidence reports from new accepted Pro sessions, comparisons of your attempts and timed debugging rounds. Public labs and this worksheet stay free. Reports are not created retroactively for earlier free solves.