Additional Coverage Prioritization
1. Introduction
When time is limited, testers often prioritize test cases to maximize requirement coverage as early as possible.
In ISTQB, one common technique is additional coverage prioritization: at each step, you select the test case that covers the largest number of currently uncovered requirements.
시간이 제한된 상황에서는 가능한 빨리 더 많은 요구사항을 커버하도록 테스트 케이스 우선순위를 정합니다.
추가 커버리지 우선순위(Additional coverage prioritization)는 매 단계마다 아직 커버되지 않은 요구사항을 가장 많이 추가로 커버하는 테스트 케이스를 선택합니다.
2. Practice Question
❓ Question
The table shows a traceability matrix from test cases to requirements. “X” means that a given test case covers the corresponding requirement.
| Req1 | Req2 | Req3 | Req4 | Req5 | Req6 | Req7 | |
|---|---|---|---|---|---|---|---|
| TC1 | X | X | X | X | |||
| TC2 | X | X | X | ||||
| TC3 | X | X | |||||
| TC4 | X |
You want to prioritize the test cases following the additional coverage prioritization technique. You execute all four test cases.
Which test case should be executed as the LAST one?
- a) TC1
- b) TC2
- c) TC3
- d) TC4
✅ Correct Answer: b) TC2
3. Explanation
Step 1: Execute the test case with the highest overall coverage first
Count how many requirements each test case covers:
- TC1: Req1, Req3, Req4, Req7 → 4 requirements
- TC2: Req1, Req3, Req5 → 3 requirements
- TC3: Req5, Req6 → 2 requirements
- TC4: Req2 → 1 requirement
So, execute TC1 first (covers 4/7).
가장 많은 요구사항을 커버하는 TC1(4개)을 먼저 실행합니다.
Step 2: Choose the test case with the highest additional coverage
After TC1, uncovered requirements are: Req2, Req5, Req6.
Now compare additional coverage:
- TC2 adds only Req5 (Req1/Req3 are already covered) → adds 1
- TC3 adds Req5 and Req6 → adds 2
- TC4 adds Req2 → adds 1
So, execute TC3 second (adds 2 new requirements).
TC1 이후 미커버 요구사항은 Req2, Req5, Req6입니다. 이 중 TC3가 Req5, Req6 두 개를 추가로 커버하므로 두 번째로 실행합니다.
Step 3: Cover the remaining uncovered requirement
After TC1 and TC3, the only requirement still uncovered is: Req2.
So, execute TC4 third (covers Req2).
남은 미커버 요구사항은 Req2 하나뿐이며, 이를 커버하는 TC4를 세 번째로 실행합니다.
Conclusion: Which test case is last?
At this point, all requirements are covered. The remaining test case to run last is TC2.
Execution order: TC1 → TC3 → TC4 → TC2
따라서 마지막으로 실행되는 테스트 케이스는 TC2입니다.
4. Summary Table
| Step | Chosen Test Case | Why? | 요약 |
|---|---|---|---|
| 1 | TC1 | Highest coverage (4 reqs) | 최대 커버 |
| 2 | TC3 | Highest additional coverage (Req5, Req6) | 추가 2개 |
| 3 | TC4 | Covers remaining Req2 | 남은 Req2 |
| 4 | TC2 | No new requirements left to add | 마지막 |
5. Final Takeaway
For the ISTQB exam, remember:
With additional coverage prioritization, always pick the test case that covers the most currently uncovered requirements. The test case that adds the least (or none) will be executed last.
시험 대비 핵심 문장입니다.
추가 커버리지 우선순위에서는 현재 미커버 요구사항을 가장 많이 추가로 커버하는 테스트를 먼저 선택한다. 추가로 커버할 것이 가장 적은 테스트가 마지막이 된다.
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