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HKDSE ICT | System Development Life Cycle Lesson Prep Guide | Six Phases, Testing, Debug Cost
Students can recite six phase names but freeze when asked for a pass rate or how much dearer a late bug is. This lesson swaps the flowchart for a schedule and a cost table.
Objectives — Students can: (1) split a 12-week project across 6 phases and name each deliverable; (2) compute a pass rate from 40 test cases and judge release readiness; (3) use the debug cost multiple to explain why testing moves earlier.
01 Prerequisites (3-minute check)
If any of these fails, fix it before the lesson starts.
| Skill | Quick check | Pass mark |
|---|---|---|
| Process | Where does development start | Requirements analysis |
| Percentages | How to compute a pass rate | Passed cases over total cases |
| Cost | What happens to the cost of a later bug | It rises |
02 Lesson flow (60 minutes)
| Time | Stage | Tutor does | Student does |
|---|---|---|---|
| 0-8 min | Split the six phases | Requirements to maintenance | One deliverable each |
| 8-20 min | Schedule | 12 weeks over 6 phases | 2 weeks each |
| 20-34 min | Testing and pass rate | 40 cases, 8 fail | Pass rate 80% |
| 34-46 min | Debug cost | Early versus late discovery | 10 times dearer |
| 46-54 min | Independent writing | A pre-release checklist | At least four items |
| 54-60 min | Exit check | Three quick questions | All three correct |
03 Teaching script (read it out)
Scene 1: Every phase has a deliverable
Requirements, design, implementation, testing, deployment, maintenance: 6 phases.
Spread evenly that is 2 weeks each over 12 weeks, but testing usually takes double: 4 weeks for testing leaves 8 for the other five.
Naming phases scores nothing; naming each deliverable does.
Spread evenly that is 2 weeks each over 12 weeks, but testing usually takes double: 4 weeks for testing leaves 8 for the other five.
Naming phases scores nothing; naming each deliverable does.
Ask the student: if testing takes 4 weeks, how many weeks per remaining phase.
Scene 2: Testing must be quantified
40 test cases, 8 failures, 32 passes (80%) and 20% failures.
Industry rule: critical functions need zero failures before release; minor ones can be patched later.
Writing testing is done gives the marks away.
Industry rule: critical functions need zero failures before release; minor ones can be patched later.
Writing testing is done gives the marks away.
Ask the student: if one failure is the login function, can you release.
Scene 3: Late bugs cost more
A defect found in requirements costs 1; found after deployment it costs about 10 times more: code changes, data fixes, user notices, reputation.
Testing aims to catch 60% before release; agile runs 3 sprints of 2 weeks (6 weeks) testing every sprint to pull discovery forward.
At 20 hours a week that is 120 hours to schedule.
Testing aims to catch 60% before release; agile runs 3 sprints of 2 weeks (6 weeks) testing every sprint to pull discovery forward.
At 20 hours a week that is 120 hours to schedule.
Ask the student: why build everything then test once is the dearest option.
04 Question types and worked steps
| Type | Example | Steps | Answer |
|---|---|---|---|
| Process | Order the phases | Order by deliverable, not preference | 6 phases |
| Calculation | Test pass rate | Passed cases over all cases | 80% |
| Calculation | Phase scheduling | Weeks over phases, weighted | 2 weeks |
| Essay | Waterfall versus agile | Two lines each with a context | One example each |
Sanity check (teach this): The six phases must add up to the total schedule; if not, a phase is missing.
A pass rate above 100 percent means the denominator is wrong.
Failures must be fewer than total cases.
Maintenance always follows deployment and cannot sit in the middle.
A pass rate above 100 percent means the denominator is wrong.
Failures must be fewer than total cases.
Maintenance always follows deployment and cannot sit in the middle.
05 Independent practice (3 questions)
| Question | Answer | What to watch |
|---|---|---|
| 12 weeks over 6 phases | 2 weeks | 12 / 6 |
| 40 cases with 8 failures, pass rate | 80% | 32 / 40 |
| Cost multiple when a bug reaches production | 10 times | Requirements stage set at 1 |
06 Common mistakes and what to say
| Mistake | Student writes | Say this |
|---|---|---|
| Reciting phase names only | Requirements, design, testing | Attach one deliverable per phase, such as a specification. |
| Writing tested with no number | No evidence | Write 40 cases at 80% pass to earn it. |
| Putting maintenance first | Wrong order | Maintenance is always last, after deployment. |
| Skipping user acceptance | Straight to release | Without UAT the 20% failure risk reaches users. |
07 Homework (paper, section and question numbers)
- Paper 1 short questions: SDLC phases (Q2-Q4) — One deliverable per phase
- Paper 2 case question: test plan (Q6) — Five test cases with expected results
- All lesson prep guides — Compare the ten-section structure across subjects
08 Exit check (last 5 minutes)
| Question | Answer | Decision |
|---|---|---|
| 12 weeks over 6 phases | 2 | Three correct means move on |
| 40 cases with 8 failures, pass rate | 80% | One miss means reteach percentages |
| Debug cost multiple after release | 10 times | Two misses means act three again |
09 Tutor FAQ
What separates waterfall from agile?
Waterfall delivers once; agile delivers per sprint and tests continuously.
What if there is no time to test everything?
Test critical functions first and document the remaining risk.
What belongs to maintenance?
Bug fixes, updates, backups and performance tuning.
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A TutorZone lesson-prep guide. Written by the TutorZone team; questions and lesson flow are original and are not taken from any school or publisher material.
