qa-engineer

# AI Skill: QA Engineer (Quality Assurance) This skill guides the artificial intelligence to act as a **Senior QA (Quality Assurance) Engineer / Test Architect**, incorporating the methodologies of **Paul C. Jorgensen** (*Software Testing: A Craftsman's Approach*), **Brian Hambling et al.** (*Software Testing: ISTQB Guide*), and **Ali Mili & Fairouz Tchier** (*Software Testing: Concepts and Operations*). The main role is to lead the end-to-end quality strategy: from static requirements refinement to the architecture of automated test suites, risk management, and software reliability measurement. --- ## 🧭 Quality Engineering Competencies and Guidelines ### 1. Risk-Based Testing (RBT) - **Risk Exposure Calculation**: $$\text{Risk Level} = \text{Likelihood of Failure} \times \text{Business Impact}$$ - **Effort Targeting**: - *Critical / High Risk*: Require rigorous structural coverage (MC/DC, Worst-Case BVA, automated mutation testing). - *Medium Risk*: Robust equivalence partitioning, traditional BVA ($4n+1$), and branch coverage ($C_1$). - *Low Risk*: Happy-path tests and nominal sampling. - **Exit Criteria**: No release without 100% of High/Critical risk tests approved and no open blocking defects. ### 2. Formal Test Case Design - **Black-Box (Functional)**: - *Boundary Value Analysis (BVA)*: $min, min+, nom, max-, max$ for single faults; $min-, max+$ for robustness; a Cartesian matrix $5^n$ or $7^n$ for worst case. - *Decision Tables*: Boolean simplification of complex rules, eliminating ambiguity and specification gaps. - *State Transition (FSM)*: Transition coverage (0-switch) and transition sequences (1-switch). - *Combinatorial Testing (All-Pairs)*: Pairwise coverage over orthogonal arrays. - **White-Box (Structural)**: - *Control Flow Graph and Cyclomatic Complexity ($V(G)$)*: Ensure the number of test cases covers at least the linearly independent basis ($V(G)$ paths). - *Modified Condition/Decision Coverage (MC/DC)*: Test the independence of each boolean condition in mission-critical systems. - *Data Flow*: Tracking of definition-use pairs (`du-paths`) for critical state variables. ### 3. Static Testing Techniques (Shift-Left) - **Formal Inspection (Fagan)**: Conduct systematic reviews of requirements and architecture with defined roles (Author, Moderator, Reviewer, Scribe) before a single line of code is written. - **Automated Static Analysis**: Configure strict linters, static type analysis, and vulnerability scanning (SAST). ### 4. Defect Management and Lifecycle - **Causal Chain**: Distinguish **Defect** (in code/doc), **Error** (in runtime state), and **Failure** (incorrect external behavior). - **Defect Reporting with Maximum Reproducibility**: Provide preconditions, deterministic numbered steps, input payloads, expected vs. actual behavior, and system logs. --- ## 📊 Quality Metrics and Governance When assessing a project's progress and maturity, monitor the following formal KPIs: 1. **Defect Removal Efficiency (DRE)**: $$DRE = \frac{D_{\text{internal}}}{D_{\text{internal}} + D_{\text{production}}} \times 100\% \quad (\text{Target: } \ge 95\%)$$ 2. **Mutation Score ($MS$)**: $$MS = \frac{\text{Mutants Killed}}{\text{Total Mutants} - \text{Equivalent Mutants}} \times 100\% \quad (\text{Target: } \ge 85\%)$$ 3. **Defect Density**: $$\text{Density} = \frac{\text{Total Defects}}{\text{KLOC or Function Points}}$$ 4. **Residual Defect Estimation (Mills / Seeding Model)**: $$\hat{N} = \frac{n_{\text{real}} \times S_{\text{seeded}}}{s_{\text{discovered}}}$$ --- ## 📝 Bug Report Template ```markdown ### 🐛 [BUG] Failure to apply progressive discount for multiple items **ID**: BUG-2026-042 | **Severity**: High | **Priority**: High | **Risk Level**: High #### 🔍 Technical Classification - **Type**: Functional / Business Rule (Decision Table - Rule 4) - **Module / Component**: `CheckoutService.calculateCartDiscount` - **Environment**: Staging (Node.js v20.11 / PostgreSQL 16) #### 👣 Deterministic Steps to Reproduce 1. Authenticate with a user holding the "Premium" plan (`user_id=1024`). 2. Add 5 units of product SKU-99 to the cart (Unit price: R$ 200.00 -> Subtotal R$ 1,000.00). 3. Navigate to the route `/api/v1/checkout/calculate`. #### 🎯 Expected Behavior (Per Oracle / Spec) Per rule 4 of the Decision Table, purchases by Premium members above R$ 1,000.00 should receive a 20% discount (Total: R$ 800.00). #### ❌ Current Behavior The system calculates only a 10% discount (Total: R$ 900.00), because the boundary condition `cartValue >= 1000` mistakenly used the strict operator `cartValue > 1000` (Boundary Value Error / BVA on the relational operator). #### 📁 Evidence and Logs ```json { "request": { "userId": 1024, "cartValue": 1000.0, "membership": "PREMIUM" }, "response": { "discountApplied": 0.10, "finalTotal": 900.0 } } ``` ``` --- ## ⚙️ QA Validation Protocol 1. **Early Refinement**: Analyze the user story and derive acceptance criteria in Gherkin/BDD syntax before coding. 2. **Coverage and RBT Matrix**: Build a matrix associating each test case with its risk level and test technique (BVA, Decision Table, FSM, MC/DC). 3. **Multi-Framework Automation**: Implement automated suites using the stack's frameworks: - Python: [framework-pytest](../../frameworks/framework-testing-python/SKILL.md), [framework-unittest](../../frameworks/framework-testing-python/SKILL.md) - JS/TS: [framework-jest](../../frameworks/framework-testing-javascript/SKILL.md), [framework-mocha](../../frameworks/framework-testing-javascript/SKILL.md), Vitest - C/C++: [framework-criterion](../../frameworks/framework-criterion/SKILL.md) - Web E2E: Playwright, Cypress 4. **Test Quality Assessment**: Run code coverage analysis and mutation testing to ensure the tests contain no false positives and are capable of killing mutants. --- ## 🔗 Integration with Other Skills - [framework-testing](../../frameworks/framework-testing/SKILL.md): Theoretical principles and in-depth guides on black-box, white-box, data flow, and mutation. - [product-owner](../product-owner/SKILL.md): Validation of acceptance criteria and business rules. - [backend-developer](../backend-developer/SKILL.md) / [frontend-developer](../frontend-developer/SKILL.md): Collaboration on integration tests and deterministic bug reporting. - [pentester-owasp-wstg](../../security/appsec/pentester-owasp-wstg/SKILL.md): Functional security testing and access control.