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Subjects · Leaving Cert Computer Science

Leaving Cert Computer Science: Testing & debugging

How often Testing & debugging comes up on the Computer Science papers, every year it was asked, and questions to try.

HL Asked on 4 of the last 5 Higher Level papers, most recently in 2025. most years

OL Asked on 4 of the last 5 Ordinary Level papers, most recently in 2025. most years

Testing & debugging, Higher Level(7 marks)

Quick ones on Testing & debugging.

(a)What kind of error is a missing colon at the end of if x > 5?
  1. Logic error
  2. Syntax error
  3. Runtime error
(b)values = [4, 8, 2]. What error does print(values[3]) raise?
  1. SyntaxError
  2. TypeError
  3. IndexError
(c)A program runs without crashing but prints the wrong average. What type of error is this?
  1. Logic error
  2. Hardware error
  3. Syntax error
Show the answers

(a) Syntax error

(b) IndexError

(c) Logic error

Your turn: Higher Level questions on Testing & debugging.

Higher Level

Asked on 4 of the last 5 Higher Level papers, most recently in 2025. most years

Every paper, year by year

YearWhere it came up
2025A9
2024A6
2023A12
2022Not asked
2021B13

Links open the State Examinations Commission’s paper for that year.

More Testing & debugging questions

Testing & debugging, 2 marks

What is system testing?

  1. Testing one function on its own
  2. Checking only the colours of the screens
  3. Testing the whole system working together
Show the answer

Testing the whole system working together

System testing checks the complete program against its requirements, after the separate units have been tested and joined together.

Testing & debugging, 2 marks

What does a breakpoint in a debugger do?

  1. Fixes the error on that line
  2. Pauses the program at a chosen line
  3. Deletes the line it is placed on
Show the answer

Pauses the program at a chosen line

At a breakpoint you can inspect the values of variables, then step through the code line by line to find where it goes wrong.

Testing & debugging, 3 marks

score has never been given a value. What error does print(score) raise?

  1. NameError
  2. TypeError
  3. IndexError
Show the answer

NameError

Python does not know the name score because nothing was ever assigned to it. A misspelt variable name causes the same NameError.

Ordinary Level

Asked on 4 of the last 5 Ordinary Level papers, most recently in 2025. most years

Every paper, year by year

YearWhere it came up
2025A12, B14
2024B13, B14
2023B14
2022B14
2021Not asked

Links open the State Examinations Commission’s paper for that year.

More Testing & debugging questions

Testing & debugging, 2 marks

A missing colon after an if line is a…

  1. Logic error
  2. Runtime error
  3. Syntax error
Show the answer

Syntax error

A syntax error breaks the rules of the language, so the program won't run at all. Python points to the line with the problem.

Testing & debugging, 2 marks

A program runs but works out the average wrongly. This is a…

  1. Hardware fault
  2. Logic error
  3. Syntax error
Show the answer

Logic error

Logic errors give wrong results with no error message, e.g. dividing by the wrong count. Trace tables and test data help find them.

Testing & debugging, 2 marks

Dividing by zero while a program is running gives a…

  1. Runtime error
  2. Syntax error
  3. Hardware fault
Show the answer

Runtime error

Runtime errors crash a program that started fine, e.g. ZeroDivisionError, IndexError, or int('abc') giving a ValueError.

Other Computer Science topics

All of Leaving Cert Computer Science