The stages of the software development life cycle (analysis, design, development, testing, evaluation and maintenance) and the use of test plans and test data.

A Unit 1 software-engineering question. Award 1 mark for each correctly described stage, to four. Analysis: the requirements of the problem are investigated and what the system must do is identified. Design: the solution is planned, including the algorithms, data structures, interface and test plan. Development (implementation): the program is written in a chosen language, building it from the design. Testing: the program is run with test data to check it works correctly and to find and fix errors. Other creditworthy stages are evaluation (judging how well the finished system meets the requirements) and maintenance (fixing problems and making improvements after release). Markers reward four distinct, correctly described stages. A common error is to merge design and development, or to leave out testing.

A Unit 1 testing question. Normal (valid) data is typical data the program should accept, which checks it works in ordinary use, for example a mark of 57 (1 mark with example). Boundary data is values at the edges of what is allowed, which checks the limits are handled correctly, for example 0 and 100 (and just outside, such as -1 and 101) (1 mark with example). Erroneous (invalid) data is data the program should reject, which checks the validation works, for example a mark of 150 or the text "abc" (1 mark with example). Testing all three types gives confidence the program behaves correctly for any input (1 mark). Markers reward the three types each with a sensible example for the 0 to 100 range. A common error is to give only normal data, missing the boundary and erroneous cases.