Did you know? A program can work for five ordinary inputs and still fail at the edge of an allowed range. G3 Computing tuition can help your child choose normal, boundary and invalid test data by starting with the task specification, predicting the correct result and comparing it with what the program actually does.
Try this first: suppose a fictional booking system accepts a whole-number group size from 1 to 30 inclusive. Ask your child what should happen for 12, 1, 30, 0 and 31 before running any code. If the expected behaviour is unclear, clarify the rule before changing the program.
The 2027 SEC G3 Computing syllabus is K349. It includes designing test cases for normal, error and boundary conditions, alongside input validation and debugging. This guide focuses on choosing useful tests; use the separate lab-exam guide for the wider Python and spreadsheet preparation plan.
Find your next learning step
Match tests to the actual requirement · Choose data with a clear purpose · Write expected results before running · Retest after a focused correction · See whether your child can explain the evidence
Match tests to the actual requirement
The official K349 syllabus connects testing with developing and refining computing solutions. A tutor should help your child explain what each test checks, rather than collect a long list of random numbers.
In our original booking example, the word inclusive matters. Both 1 and 30 are acceptable. Replacing an inclusive comparison with a strict comparison could reject a legitimate booking even though 12 still works.
Read the specification together and underline the permitted type, limits and required response to invalid input. Different tasks can require different error handling; the example is a practice illustration, not an examination template.
Choose data with a clear purpose
A normal test such as 12 checks an ordinary valid case. Boundary tests such as 1 and 30 check the accepted limits. Values just outside the range, such as 0 and 31, check rejection near those limits.
An invalid test is not automatically a boundary test. If whole numbers are required, 2.5 is invalid for a different reason. A blank entry or a word may be useful when the specification requires the program to handle those inputs.
Ask your child to label the condition being tested. One input can test more than one condition, but the explanation should make its purpose clear. Avoid claiming that a single successful run proves the program correct.
Write expected results before running
For this fictional interactive system, assume the stated rule is to ask again after an invalid entry. The expected results are: 12 accepted, 1 accepted, 30 accepted, 0 rejected with another prompt, and 31 rejected with another prompt.
Make a small test record with input, purpose, expected result, actual result and outcome. If 30 is rejected, inspect the upper-limit comparison. If 31 is accepted, inspect the range check and the path through the decision.
A tutor can model one test and then let the student complete the others. The useful skill is connecting an observed failure to a possible cause, rather than immediately replacing the whole program.
Retest after a focused correction
After correcting a comparison, rerun the failed case and the neighbouring cases. A change that repairs 30 should still reject 31 and keep 1 valid. This is a practical way to check that the correction has not introduced another problem.
Separate an input-validation problem from a calculation problem. Correctly rejecting an impossible group size does not establish that the program calculates the price correctly for valid bookings.
Then change the practice task to a different allowed range. Your child should choose fresh tests from the new rule, rather than carry over the old numbers without thinking.
See whether your child can explain the evidence
Bring a short program and its test record to a consultation. Ask whether the difficulty is reading the requirement, selecting cases, predicting outputs or interpreting failures.
At home, one useful question is: “Which mistake would this input help you discover?” A clear answer reveals more than a large number of repeated runs.
Progress means your child can justify a small, purposeful set of tests and revise it when requirements change. Specialist Computing support should be confirmed with the provider before booking.
Choose a focused next step
Continue with the G3 Computing lab-exam preparation guide, or browse the Primary, PSLE and SEC syllabus directory for another learning question.
For parents in Punggol, bring the exact subject, examination year and a recent piece of work to a consultation. Ask which specific difficulty the proposed lessons will address, how practice will fit the school week, and what independent progress should look like.
For an example of diagnosis and focused 3-pax Mathematics support, see the Secondary 1 Mathematics tutor guide for Clementi. Confirm subject availability and arrangements with the provider; that Mathematics programme does not establish availability of specialist subjects in Punggol.
Official syllabus checked 10 October 2026. The worked examples and practice routines are original teaching illustrations, not SEAB questions, official model answers or promises of examination results.
