testing-guide

name	testing-guide
description	Guides test writing with AAA pattern, BVA, EP, and edge case analysis. Use when writing unit tests, integration tests, or infrastructure validation tests.

Testing Guide

Apply when: "테스트 작성", "테스트 추가", "test", "write test"

Structure (AAA Pattern)

def test_<target>_<condition>_<expected>():
    # Arrange
    ...
    # Act
    ...
    # Assert
    ...

FIRST Principles

• Fast: no external I/O
• Isolated: no dependency between tests
• Repeatable: same result every run
• Self-validating: assert determines pass/fail
• Timely: written with production code

Boundary Value Analysis (BVA)

For any range [min, max], always test:

• min-1, min, min+1, max-1, max, max+1

Equivalence Partitioning (EP)

• Identify valid/invalid partitions
• Pick 1 representative from each partition
• Include: None, empty string, empty list

Coverage Target

• Branch coverage priority (both if/else)
• Exception paths (try/except, raise conditions)
• Normal path + error path

pytest Rules

• @pytest.mark.parametrize for multiple inputs
• @pytest.fixture for shared setup
• pytest.raises() for exception verification
• File: test_<module>.py
• Function: test_<target>_<condition>_<expected>()

Mock Rules

• External API, DB, filesystem → Mock
• Pure logic functions → no Mock
• Use unittest.mock.patch

Test Type Selection

Request	Test Type
Function/class	Unit test (BVA + EP)
Module integration	Integration test
Bug fix	Regression test (reproduce bug)
API endpoint	Integration + status code

Checklist (every test)

• Happy path
• Error case (invalid input, exception)
• Boundary values (min, max, min-1, max+1)
• Empty input (None, "", [])
• Edge cases (see 5-axis below)
• Idempotency (if applicable)

Edge Case Analysis (5-axis)

Derive edge cases from 5 axes. Pick at least 1 from each applicable axis.

Axis	Question	Examples
Input	Empty, max length, special chars?	null, 0, MAX_INT, unicode, newline
Environment	Disk full, OOM, network down?	DNS fail, read-only mount, low bandwidth
State	Initial, mid-failure, post-restart?	uninitialized, partial write, cold start
Time	Concurrency, timeout, order reversal?	simultaneous write, expired token
Resource	Exhaustion, contention, limit reached?	FD exhausted, pool full, PID limit

Reference: file:///root/32_system-engineering-resources/01_fundamentals/cs/testing/04_test_design/edge_case_testing.md

Terminology

Term	Meaning
Edge case	Boundary of valid range
Corner case	Multiple boundaries intersecting
Degenerate case	Extremely simple/empty input
Race condition	Timing-dependent concurrent conflict

Infrastructure Testing

대상	검증 명령어
Terraform syntax	terraform validate
Terraform format	terraform fmt -check
Terraform plan	terraform plan (No unexpected changes)
Ansible syntax	ansible-playbook --syntax-check
Ansible dry-run	ansible-playbook --check --diff
Shell scripts	shellcheck <script>.sh
Shell syntax	bash -n <script>.sh

IaC Test Principles

• terraform plan before every apply
• ansible --check before every run
• Idempotency: re-run produces no changes
• Validate after apply: health check, resource state query
• Test failure → switch to skill://debugging-and-recovery

Container / Docker Testing

대상	검증 명령어
Dockerfile lint	hadolint Dockerfile
Image build	docker build --no-cache -t test .
Container health	docker inspect --format='{{.State.Health.Status}}'
Compose syntax	docker compose config
Port binding	ss -tlnp 으로 포트 확인

Post-Change Verification Pattern

변경 후 반드시 실행하는 검증 순서:

# 1. 문법/구문 검증
terraform validate && terraform fmt -check
ansible-playbook --syntax-check site.yml
bash -n script.sh && shellcheck script.sh

# 2. Dry-run
terraform plan
ansible-playbook --check --diff site.yml

# 3. 적용 후 상태 확인
terraform plan  # "No changes" 확인
curl -f http://endpoint/health
aws ec2 describe-instance-status --instance-ids <id>

Red Flags

• 테스트 없이 "동작 확인했습니다" 주장
• happy path만 테스트하고 에러 케이스 누락
• edge case 도출 없이 "정상 동작" 판단
• terraform plan 미확인 상태에서 apply
• 테스트 실패를 무시하고 진행
• "나중에 테스트 추가하겠습니다"로 건너뜀