1. Introduction
This question asks you to apply Equivalence Partitioning (EP) to determine the minimum number of valid test cases needed for full coverage.
EP is used to minimize test effort by dividing input data into partitions representing similar behavior.
동등 분할(EP)은 입력값을 유사 행동을 가진 그룹으로 나누어 최소한의 테스트로 최대 커버리지를 달성하는 기법입니다.
2. Problem Summary
Search form has two criteria:
- Floor (3 partitions)
- Ground floor
- First floor
- Second or higher floor
- Garden type (3 partitions)
- No garden
- Small garden
- Large garden
Constraint:
Only ground-floor apartments can have a garden.
제약 조건: 정원은 오직 1층(ground floor)에만 존재합니다.
The form blocks invalid combinations automatically, so we focus ONLY on valid partitions.
3. EP Analysis
Question
✔ Garden type validity per floor
| Floor | No Garden | Small Garden | Large Garden |
|---|---|---|---|
| Ground floor | ✔ Valid | ✔ Valid | ✔ Valid |
| First floor | ✔ Valid | ❌ Invalid | ❌ Invalid |
| Second or higher | ✔ Valid | ❌ Invalid | ❌ Invalid |
✔ Goal: Cover all valid EP partitions
- Garden partitions to cover: no garden, small garden, large garden
- Floor partitions to cover: ground, first, second-or-higher
✔ Key Insight
Small garden / large garden are ONLY valid with ground floor, so we need two tests for those. First floor and second-or-higher can only be paired with “no garden”.
4. Minimal Test Set (4 Tests)
| TC # | Floor | Garden Type | Partition Covered |
|---|---|---|---|
| TC1 | Ground floor | Small garden | Garden: small |
| TC2 | Ground floor | Large garden | Garden: large |
| TC3 | First floor | No garden | Floor: first |
| TC4 | Second or higher | No garden | Floor: second/higher |
5. Correct Answer
✅ Correct Answer: b) 4
📘 Explanation (EN/KR)
-
Small and large garden → must pair with ground floor → need 2 cases.
작은/큰 정원은 반드시 1층과 조합되어야 하므로 각각 1개씩 필요(2개). -
First floor needs 1 test (with “no garden”).
첫 번째 층은 ‘정원 없음’과 함께 1개 필요. -
Second-or-higher needs 1 test (with “no garden”).
2층 이상도 ‘정원 없음’과 함께 1개 필요.
✔ Total = 4 test cases → option (b)
✔ 총 4개 → 정답은 (b)
Equivalence Partitioning (EP)
1. What is Equivalence Partitioning (EP)?
Equivalence Partitioning (EP) is a black-box test design technique where input values are divided into groups (partitions) that are expected to behave in the same way.
동등 분할(EP)은 입력값을 같은 동작을 만드는 그룹(Partition)으로 나누어, 각 그룹을 대표하는 최소 테스트를 선택하는 블랙박스 기법입니다.
2. Why Use EP?
- Reduces number of test cases
필요한 테스트 수를 줄여줌 - Ensures essential coverage
중요한 입력 범위를 빠짐없이 테스트 - Simple and effective for forms, ranges, categories
폼 입력, 범위 체크, 카테고리 구분 등에 효과적
3. EP Rule Summary
✔ EP 핵심 규칙 (EN/KR)
- Each partition must be tested at least once.
각 파티션은 최소 1번 테스트해야 한다. - Choose ONE representative test per partition.
각 파티션에서 대표값 하나만 선택한다. - Include both valid and invalid partitions.
유효/무효 파티션 모두 고려한다. - Invalid partitions each require separate tests.
무효 파티션은 각각 별도의 테스트가 필요하다.
4. EP Example – Simple Numerical Input
Suppose a field accepts age 1–120.
| Partition Type | Range | Valid? | Representative |
|---|---|---|---|
| Invalid low | < 1 | No | 0 |
| Valid | 1–120 | Yes | 30 |
| Invalid high | > 120 | No | 150 |
✔ Total = 3 test cases (one per partition)
✔ 총 3개 테스트 (각 파티션 1개씩)
5. EP Example – Categorical Inputs
Consider three valid categories:
- Bronze
- Silver
- Gold
Each category = one valid partition.
✔ Total = 3 tests ✔ 총 3개 테스트
6. EP Example – ISTQB Exam Case (Apartment Search)
This is the exact logic used in Exam A Q20.
Inputs:
- Floor: Ground / First / Second+
- Garden: None / Small / Large
Constraint:
Only ground-floor apartments can have gardens.
정원은 오직 1층만 가능
Minimal EP Tests:
| Test | Floor | Garden | Partition Covered |
|---|---|---|---|
| TC1 | Ground | Small | Garden: small |
| TC2 | Ground | Large | Garden: large |
| TC3 | First | No garden | Floor: first |
| TC4 | Second+ | No garden | Floor: second+ |
✔ Total = 4 test cases ✔ 총 4개 테스트
7. EP vs Other Techniques
| Technique | Type | Used For | Main Benefit |
|---|---|---|---|
| EP | Black-box | Ranges & categories | Few tests, broad coverage |
| Boundary Value Analysis | Black-box | Numeric ranges | Best for off-by-one defects |
| Decision Table | Black-box | Rules & combinations | Captures complex logic |
| State Transition | Black-box | Systems with states | Ensures valid/invalid transitions |
8. ISTQB Exam Tips
- One test per partition – always the minimal rule 각 파티션당 1개가 최소
- Check constraints – some combinations become invalid 제약 조건에 따라 무효 조합 발생
- Invalid partitions do NOT combine (must be separate tests) 무효 파티션은 절대 묶이지 않음 → 각자 테스트 필요
- EP answers tend to be small numbers (3–6 range) EP 정답은 보통 3~6개 사이
9. Final Summary
- EP = divide inputs into partitions with the same behavior
EP = 동일 행동을 보이는 입력 그룹으로 분할 - Choose ONE test per partition
각 파티션에서 하나만 선택 - Include valid + invalid partitions
유효/무효 모두 필요 - Constraints change the valid combinations
제약 조건이 유효 조합을 바꾼다
EP vs BVA vs Decision Table
1. Introduction
This post provides a full comparison of three major black-box test design techniques: Equivalence Partitioning (EP), Boundary Value Analysis (BVA), and Decision Table Testing. These techniques frequently appear in ISTQB exam questions.
이 글은 ISTQB 시험에 가장 자주 등장하는 세 가지 블랙박스 기법: EP(동등 분할), BVA(경계값 분석), Decision Table(결정 테이블)을 하나로 비교 정리한 포스트입니다.
2. Technique Definitions
✔ Equivalence Partitioning (EP)
Divide inputs into partitions where each partition represents a set of values expected to behave the same.
입력을 동등한 행동을 보이는 그룹(Partition)으로 나누고, 각 그룹에서 대표값 1개만 테스트하는 기법.
✔ Boundary Value Analysis (BVA)
Focus on values at the edges (min/max) of input ranges where defects are most likely to occur.
입력 범위의 경계(최소/최대) 주변에서 결함이 가장 많이 발생한다는 원리를 이용하는 기법.
✔ Decision Table Testing (DT)
Validate combinations of multiple conditions and their expected actions.
여러 조건(조건식) 조합에 따른 결과(Action)를 체계적으로 테스트하는 비즈니스 규칙 기반 기법.
3. Comparative Summary Table
| Technique | Type | Best For | Test Basis | Typical No. of Tests | Key Benefit |
|---|---|---|---|---|---|
| EP | Black-box | Ranges & categories | Input partitions | Low (3–6) | Minimizes tests while keeping coverage |
| BVA | Black-box | Numeric boundaries | Min/max boundary points | Medium (4–6) | Finds off-by-one & edge errors |
| Decision Table | Black-box | Business rules & combinations | Conditions × Actions | Varies (depends on rules) | Full coverage of rule combinations |
✔ EP = 입력 그룹 분할 ✔ BVA = 경계값 중심 테스트 ✔ Decision Table = 조건 조합 테스트
4. When to Use Each Technique
✔ Use EP when…
- Input values fall into categories or ranges
- You want minimal test cases
- Only one value per group is needed
범주/구간 입력이 있을 때, 최소 테스트로 커버하고 싶을 때 사용
✔ Use BVA when…
- Input fields have numeric boundaries
- Edge cases are likely to fail
- You want to detect off-by-one defects
숫자 범위·최소/최대 처리 테스트에 적합
✔ Use Decision Table when…
- System behavior depends on rule combinations
- Multiple conditions influence the output
- You need to ensure no rule is missing
여러 조건 조합이 필요한 비즈니스 규칙 테스트에 적합
5. Example Comparison
EP Example – Age
Age allowed: 1–120
- Invalid low: < 1
- Valid: 1–120
- Invalid high: > 120
✔ 3 tests needed
BVA Example – Age
Same range: 1–120
- 0, 1, 2
- 119, 120, 121
✔ 6 tests recommended
Decision Table Example – Discount Rules
| Rule 1 | Rule 2 | Rule 3 | Rule 4 | |
|---|---|---|---|---|
| Member? | Y | Y | N | N |
| Amount > 100? | Y | N | Y | N |
| Action | 20% discount | 10% discount | 10% discount | No discount |
✔ 4 tests (one per rule)
6. Combined Exam Tips
- EP = 1 test per partition
- BVA = min–1, min, min+1, max–1, max, max+1
- Decision Table = each column = 1 test case
- EP + BVA are often paired in ISTQB exam questions
- Decision Table is used when multiple conditions interact
- Constraints change partitions → adjust EP tests accordingly
EP는 파티션당 1개, BVA는 경계값 중심, Decision Table은 조합당 1개라는 원칙을 꼭 기억하세요.
7. Final Summary
- EP → Input grouping 입력값 그룹화
- BVA → Boundary edges 경계값 중심
- Decision Table → Condition combinations 조건 조합 중심
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