Home · IGCSE Computer Science 0478 · Algorithm design and problem-solving · Normal, abnormal, extreme and boundary test data · Practice
IGCSE · Practice questions · Normal, abnormal, extreme and boundary test data

Accepted or rejected?

Six original Cambridge-style questions on choosing and using test data.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.
Keep these straight

Find the limits first.

01
Recall
[4 marks]

State the purpose of each type of test data: normal, abnormal, extreme and boundary.

  • Normal: to check typical data is accepted and processed correctly. ✓
  • Abnormal: to check data that should be rejected is rejected. ✓
  • Extreme: to check the largest and smallest acceptable values are accepted. ✓
  • Boundary: to check each limit, the last accepted value is accepted and the first value beyond it is rejected. ✓
02
Apply
[4 marks]

A program accepts the number of pupils on a school trip, from 5 to 40 inclusive. Give one item of normal, abnormal and extreme test data, and one boundary pair, with the expected result for each.

  • Normal: e.g. 20, accepted. ✓
  • Abnormal: e.g. 75 or "ten", rejected. ✓
  • Extreme: 5 or 40, accepted. ✓
  • Boundary: 40 accepted and 41 rejected (or 5 accepted and 4 rejected). ✓
03
Explain
[2 marks]

Explain the difference between extreme test data and boundary test data.

  • Extreme data is only the largest/smallest acceptable value, which should be accepted. ✓
  • Boundary data also includes the matching value just outside the limit, which should be rejected. ✓
04
Analysis
[3 marks]

A program should accept heights from 100 to 220 cm. It is tested with 150, 180 and 200 only. Explain why this testing is not enough, and suggest three more items of test data.

  • All three are normal data, so the limits and invalid data are not tested. ✓
  • Add extreme / boundary data, e.g. 100 and 220 (accepted), 99 and 221 (rejected). ✓
  • Add abnormal data, e.g. -50 or "tall" (rejected). (Any three suitable values.) ✓
05
Apply
[2 marks]

A password must have from 8 to 16 characters. Give boundary test data for the lower limit and the expected results.

  • A password of 8 characters: accepted. ✓
  • A password of 7 characters: rejected. ✓
06
Analysis
[2 marks]

This check is meant to accept scores from 0 to 10 inclusive: IF Score > 0 AND Score < 10 THEN OUTPUT "Valid". Identify the test data that would show it is wrong and correct the condition.

  • Testing the extreme values 0 and 10 shows they are wrongly rejected. ✓
  • Correct condition: Score >= 0 AND Score <= 10. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.