Debugging (Spot the Mistake)
9 free practice questions with explanations
PassNova has 9 free Kids Coding & Logic practice questions on Debugging (Spot the Mistake), each with a clear explanation. Practise them in the browser with instant feedback — 100% free, no sign-up, on any device. Updated for 2026.
Debugging (Spot the Mistake): example questions & answers
9 worked examples with answers and explanations below. Practise them in the browser with instant feedback on every answer.
Debugging means finding the mistake. Steps to make toast: 1) Put bread in toaster, 2) Eat the toast, 3) Turn toaster on. Which step is in the WRONG place?
- ATurn toaster on
- BNone of them
- CEat the toast✓
- DPut bread in toaster
Answer: You can't eat the toast before it is even toasted, so that step is out of order.
A pattern should be red, yellow, red, yellow but someone wrote red, yellow, red, red. Where is the mistake?
- AThe last shape should be yellow, not red✓
- BThere is no mistake
- CThe whole pattern is correct
- DThe first shape is wrong
Answer: The pattern breaks at the end where an extra red appears instead of a yellow.
What does 'debugging' mean?
- AAdding more bugs
- BFinding and fixing mistakes✓
- CTurning off the computer
- DDrawing a picture
Answer: Debugging means looking for mistakes and fixing them so things work correctly.
Counting steps: 1, 2, 3, 5, 6. Which number was missed by mistake?
- A7
- B1
- C4✓
- D6
Answer: The number 4 is missing because it should come between 3 and 5.
A robot is told to draw a triangle but keeps drawing 4 sides. What is the likely mistake in its steps?
- ATriangles need 4 sides
- BIt repeats the drawing step too many times✓
- CThe paper is too small
- DIt doesn't have a pencil
Answer: A triangle has 3 sides, so repeating the step 4 times is the mistake to fix.
Instructions to wash hands: 1) Turn on tap, 2) Dry hands, 3) Wash hands with soap. What should you fix?
- ASwap steps 2 and 3 so you wash before you dry✓
- BRemove step 1
- CAdd more drying
- DNothing is wrong
Answer: You must wash your hands before drying them, so steps 2 and 3 are in the wrong order.
A robot should go: forward, forward, turn left. It went forward, turn left, forward and ended in the wrong place. What was the bug?
- AThe robot was too big
- BIt was the right path
- CIt moved too fast
- DThe turn happened too early✓
Answer: The turn was in the wrong spot, so fixing the order puts the turn after two forwards.
If your code doesn't work, what is a smart thing to do?
- ACheck each step carefully to find the mistake✓
- BDelete everything
- CGive up right away
- DBlame the computer
Answer: Checking each step helps you spot and fix the bug, which is what good debugging is.
A song counts: 'One, two, four, five'. Which number is missing?
- AOne
- BSix
- CThree✓
- DFive
Answer: The number three is missing because it should come between two and four.