ISTQB 연습문제 풀이 - Exam A : Q#21


1. Introduction

This question evaluates how much 2-value Boundary Value Analysis (BVA) coverage is achieved for a grading system based on point ranges.

본 문제는 점수 구간에 따른 학점 시스템에서 현재 테스트 케이스가 2값 경계값 분석(BVA)을 얼마나 충족하는지를 묻는 문제입니다.

2. Final Grade Rules

Grades are assigned as follows:

Range Grade
0–50failed
51–60fair
61–70satisfactory
71–80good
81–90very good
91–100excellent

3. Test Cases Provided

Test Case Final Result Expected Grade
TC191excellent
TC250failed
TC381very good
TC460fair
TC570satisfactory
TC680good

4. Boundary Value Analysis

(Question)
What is the 2-value boundary value analysis (BVA) coverage for the final result that is achieved with the existing test cases?

a) 50%   b) 60%   c) 33.3%   d) 100%

✔ 2-value BVA Boundary Points

Each range boundary produces two boundary values: the boundary itself and the next value (either +1 or –1 depending on direction).

All boundaries (12 total):
0, 50, 51, 60, 61, 70, 71, 80, 81, 90, 91, 100

총 12개의 2값 경계값이 존재합니다.

✔ Coverage from existing test cases

Current test cases cover these boundary points:

  • 50 (TC2)
  • 60 (TC4)
  • 70 (TC5)
  • 80 (TC6)
  • 81 (TC3)
  • 91 (TC1)

→ 6 out of 12 boundaries covered
→ 50% coverage

테스트 케이스가 12개의 경계 중 6개를 커버하므로 커버리지는 50%입니다.

5. Correct Answer

✅ Correct Answer: a) 50%

📘 Explanation (EN/KR)

  • There are 12 total BVA boundary values.
  • The existing tests cover 6 of them.
  • Therefore: 6 / 12 = 50%.

총 12개 경계 중 6개만 테스트되었으므로 커버리지는 정확히 50% → 정답은 (a)

6. Final Summary

  • 2-value BVA checks boundaries and their immediate neighbors.
  • This grading system produces 12 such boundary values.
  • Current tests cover exactly half of them.

경계값을 정확히 나누면 계산이 매우 쉬워지는 문제 유형입니다. FL-4.2.2


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