docs: tea in 4; Diátaxis (#1320)

* docs: tea in 4; Diátaxis * docs: addressed review comments * docs: refined the docs
2026-01-30 04:32:02 +00:00 · 2026-01-15 13:18:37 -06:00
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+---
+title: "Risk-Based Testing Explained"
+description: Understanding how TEA uses probability × impact scoring to prioritize testing effort
+---
+
+# Risk-Based Testing Explained
+
+Risk-based testing is TEA's core principle: testing depth scales with business impact. Instead of testing everything equally, focus effort where failures hurt most.
+
+## Overview
+
+Traditional testing approaches treat all features equally:
+- Every feature gets same test coverage
+- Same level of scrutiny regardless of impact
+- No systematic prioritization
+- Testing becomes checkbox exercise
+
+**Risk-based testing asks:**
+- What's the probability this will fail?
+- What's the impact if it does fail?
+- How much testing is appropriate for this risk level?
+
+**Result:** Testing effort matches business criticality.
+
+## The Problem
+
+### Equal Testing for Unequal Risk
+
+```markdown
+Feature A: User login (critical path, millions of users)
+Feature B: Export to PDF (nice-to-have, rarely used)
+
+Traditional approach:
+- Both get 10 tests
+- Both get same review scrutiny
+- Both take same development time
+
+Problem: Wasting effort on low-impact features while under-testing critical paths.
+```
+
+### No Objective Prioritization
+
+```markdown
+PM: "We need more tests for checkout"
+QA: "How many tests?"
+PM: "I don't know... a lot?"
+QA: "How do we know when we have enough?"
+PM: "When it feels safe?"
+
+Problem: Subjective decisions, no data, political debates.
+```
+
+## The Solution: Probability × Impact Scoring
+
+### Risk Score = Probability × Impact
+
+**Probability** (How likely to fail?)
+- **1 (Low):** Stable, well-tested, simple logic
+- **2 (Medium):** Moderate complexity, some unknowns
+- **3 (High):** Complex, untested, many edge cases
+
+**Impact** (How bad if it fails?)
+- **1 (Low):** Minor inconvenience, few users affected
+- **2 (Medium):** Degraded experience, workarounds exist
+- **3 (High):** Critical path broken, business impact
+
+**Score Range:** 1-9
+
+#### Risk Scoring Matrix
+
+```mermaid
+%%{init: {'theme':'base', 'themeVariables': { 'fontSize':'14px'}}}%%
+graph TD
+    subgraph Matrix[" "]
+        direction TB
+        subgraph Impact3["Impact: HIGH (3)"]
+            P1I3["Score: 3<br/>Low Risk"]
+            P2I3["Score: 6<br/>HIGH RISK<br/>Mitigation Required"]
+            P3I3["Score: 9<br/>CRITICAL<br/>Blocks Release"]
+        end
+        subgraph Impact2["Impact: MEDIUM (2)"]
+            P1I2["Score: 2<br/>Low Risk"]
+            P2I2["Score: 4<br/>Medium Risk"]
+            P3I2["Score: 6<br/>HIGH RISK<br/>Mitigation Required"]
+        end
+        subgraph Impact1["Impact: LOW (1)"]
+            P1I1["Score: 1<br/>Low Risk"]
+            P2I1["Score: 2<br/>Low Risk"]
+            P3I1["Score: 3<br/>Low Risk"]
+        end
+    end
+
+    Prob1["Probability: LOW (1)"] -.-> P1I1
+    Prob1 -.-> P1I2
+    Prob1 -.-> P1I3
+
+    Prob2["Probability: MEDIUM (2)"] -.-> P2I1
+    Prob2 -.-> P2I2
+    Prob2 -.-> P2I3
+
+    Prob3["Probability: HIGH (3)"] -.-> P3I1
+    Prob3 -.-> P3I2
+    Prob3 -.-> P3I3
+
+    style P3I3 fill:#f44336,stroke:#b71c1c,stroke-width:3px,color:#fff
+    style P2I3 fill:#ff9800,stroke:#e65100,stroke-width:2px,color:#000
+    style P3I2 fill:#ff9800,stroke:#e65100,stroke-width:2px,color:#000
+    style P2I2 fill:#fff9c4,stroke:#f57f17,stroke-width:1px,color:#000
+    style P1I1 fill:#c8e6c9,stroke:#2e7d32,stroke-width:1px,color:#000
+    style P2I1 fill:#c8e6c9,stroke:#2e7d32,stroke-width:1px,color:#000
+    style P3I1 fill:#c8e6c9,stroke:#2e7d32,stroke-width:1px,color:#000
+    style P1I2 fill:#c8e6c9,stroke:#2e7d32,stroke-width:1px,color:#000
+    style P1I3 fill:#c8e6c9,stroke:#2e7d32,stroke-width:1px,color:#000
+```
+
+**Legend:**
+- 🔴 Red (Score 9): CRITICAL - Blocks release
+- 🟠 Orange (Score 6-8): HIGH RISK - Mitigation required
+- 🟡 Yellow (Score 4-5): MEDIUM - Mitigation recommended
+- 🟢 Green (Score 1-3): LOW - Optional mitigation
+
+### Scoring Examples
+
+**Score 9 (Critical):**
+```
+Feature: Payment processing
+Probability: 3 (complex third-party integration)
+Impact: 3 (broken payments = lost revenue)
+Score: 3 × 3 = 9
+
+Action: Extensive testing required
+- E2E tests for all payment flows
+- API tests for all payment scenarios
+- Error handling for all failure modes
+- Security testing for payment data
+- Load testing for high traffic
+- Monitoring and alerts
+```
+
+**Score 1 (Low):**
+```
+Feature: Change profile theme color
+Probability: 1 (simple UI toggle)
+Impact: 1 (cosmetic only)
+Score: 1 × 1 = 1
+
+Action: Minimal testing
+- One E2E smoke test
+- Skip edge cases
+- No API tests needed
+```
+
+**Score 6 (Medium-High):**
+```
+Feature: User profile editing
+Probability: 2 (moderate complexity)
+Impact: 3 (users can't update info)
+Score: 2 × 3 = 6
+
+Action: Focused testing
+- E2E test for happy path
+- API tests for CRUD operations
+- Validation testing
+- Skip low-value edge cases
+```
+
+## How It Works in TEA
+
+### 1. Risk Categories
+
+TEA assesses risk across 6 categories:
+
+**TECH** - Technical debt, architecture fragility
+```
+Example: Migrating from REST to GraphQL
+Probability: 3 (major architectural change)
+Impact: 3 (affects all API consumers)
+Score: 9 - Extensive integration testing required
+```
+
+**SEC** - Security vulnerabilities
+```
+Example: Adding OAuth integration
+Probability: 2 (third-party dependency)
+Impact: 3 (auth breach = data exposure)
+Score: 6 - Security testing mandatory
+```
+
+**PERF** - Performance degradation
+```
+Example: Adding real-time notifications
+Probability: 2 (WebSocket complexity)
+Impact: 2 (slower experience)
+Score: 4 - Load testing recommended
+```
+
+**DATA** - Data integrity, corruption
+```
+Example: Database migration
+Probability: 2 (schema changes)
+Impact: 3 (data loss unacceptable)
+Score: 6 - Data validation tests required
+```
+
+**BUS** - Business logic errors
+```
+Example: Discount calculation
+Probability: 2 (business rules complex)
+Impact: 3 (wrong prices = revenue loss)
+Score: 6 - Business logic tests mandatory
+```
+
+**OPS** - Operational issues
+```
+Example: Logging system update
+Probability: 1 (straightforward)
+Impact: 2 (debugging harder without logs)
+Score: 2 - Basic smoke test sufficient
+```
+
+### 2. Test Priorities (P0-P3)
+
+Risk scores inform test priorities (but aren't the only factor):
+
+**P0 - Critical Path**
+- **Risk Scores:** Typically 6-9 (high risk)
+- **Other Factors:** Revenue impact, security-critical, regulatory compliance, frequent usage
+- **Coverage Target:** 100%
+- **Test Levels:** E2E + API
+- **Example:** Login, checkout, payment processing
+
+**P1 - High Value**
+- **Risk Scores:** Typically 4-6 (medium-high risk)
+- **Other Factors:** Core user journeys, complex logic, integration points
+- **Coverage Target:** 90%
+- **Test Levels:** API + selective E2E
+- **Example:** Profile editing, search, filters
+
+**P2 - Medium Value**
+- **Risk Scores:** Typically 2-4 (medium risk)
+- **Other Factors:** Secondary features, admin functionality, reporting
+- **Coverage Target:** 50%
+- **Test Levels:** API happy path only
+- **Example:** Export features, advanced settings
+
+**P3 - Low Value**
+- **Risk Scores:** Typically 1-2 (low risk)
+- **Other Factors:** Rarely used, nice-to-have, cosmetic
+- **Coverage Target:** 20% (smoke test)
+- **Test Levels:** E2E smoke test only
+- **Example:** Theme customization, experimental features
+
+**Note:** Priorities consider risk scores plus business context (usage frequency, user impact, etc.). See [Test Priorities Matrix](/docs/reference/tea/knowledge-base.md#test-priorities-matrix) for complete criteria.
+
+### 3. Mitigation Plans
+
+**Scores ≥6 require documented mitigation:**
+
+```markdown
+## Risk Mitigation
+
+**Risk:** Payment integration failure (Score: 9)
+
+**Mitigation Plan:**
+- Create comprehensive test suite (20+ tests)
+- Add payment sandbox environment
+- Implement retry logic with idempotency
+- Add monitoring and alerts
+- Document rollback procedure
+
+**Owner:** Backend team lead
+**Deadline:** Before production deployment
+**Status:** In progress
+```
+
+**Gate Rules:**
+- **Score = 9** (Critical): Mandatory FAIL - blocks release without mitigation
+- **Score 6-8** (High): Requires mitigation plan, becomes CONCERNS if incomplete
+- **Score 4-5** (Medium): Mitigation recommended but not required
+- **Score 1-3** (Low): No mitigation needed
+
+## Comparison: Traditional vs Risk-Based
+
+### Traditional Approach
+
+```typescript
+// Test everything equally
+describe('User profile', () => {
+  test('should display name');
+  test('should display email');
+  test('should display phone');
+  test('should display address');
+  test('should display bio');
+  test('should display avatar');
+  test('should display join date');
+  test('should display last login');
+  test('should display theme preference');
+  test('should display language preference');
+  // 10 tests for profile display (all equal priority)
+});
+```
+
+**Problems:**
+- Same effort for critical (name) vs trivial (theme)
+- No guidance on what matters
+- Wastes time on low-value tests
+
+### Risk-Based Approach
+
+```typescript
+// Test based on risk
+
+describe('User profile - Critical (P0)', () => {
+  test('should display name and email');  // Score: 9 (identity critical)
+  test('should allow editing name and email');
+  test('should validate email format');
+  test('should prevent unauthorized edits');
+  // 4 focused tests on high-risk areas
+});
+
+describe('User profile - High Value (P1)', () => {
+  test('should upload avatar');  // Score: 6 (users care about this)
+  test('should update bio');
+  // 2 tests for high-value features
+});
+
+// P2: Theme preference - single smoke test
+// P3: Last login display - skip (read-only, low value)
+```
+
+**Benefits:**
+- 6 focused tests vs 10 unfocused tests
+- Effort matches business impact
+- Clear priorities guide development
+- No wasted effort on trivial features
+
+## When to Use Risk-Based Testing
+
+### Always Use For:
+
+**Enterprise projects:**
+- High stakes (revenue, compliance, security)
+- Many features competing for test effort
+- Need objective prioritization
+
+**Large codebases:**
+- Can't test everything exhaustively
+- Need to focus limited QA resources
+- Want data-driven decisions
+
+**Regulated industries:**
+- Must justify testing decisions
+- Auditors want risk assessments
+- Compliance requires evidence
+
+### Consider Skipping For:
+
+**Tiny projects:**
+- 5 features total
+- Can test everything thoroughly
+- Risk scoring is overhead
+
+**Prototypes:**
+- Throw-away code
+- Speed over quality
+- Learning experiments
+
+## Real-World Example
+
+### Scenario: E-Commerce Checkout Redesign
+
+**Feature:** Redesigning checkout flow from 5 steps to 3 steps
+
+**Risk Assessment:**
+
+| Component | Probability | Impact | Score | Priority | Testing |
+|-----------|-------------|--------|-------|----------|---------|
+| **Payment processing** | 3 | 3 | 9 | P0 | 15 E2E + 20 API tests |
+| **Order validation** | 2 | 3 | 6 | P1 | 5 E2E + 10 API tests |
+| **Shipping calculation** | 2 | 2 | 4 | P1 | 3 E2E + 8 API tests |
+| **Promo code validation** | 2 | 2 | 4 | P1 | 2 E2E + 5 API tests |
+| **Gift message** | 1 | 1 | 1 | P3 | 1 E2E smoke test |
+
+**Test Budget:** 40 hours
+
+**Allocation:**
+- Payment (Score 9): 20 hours (50%)
+- Order validation (Score 6): 8 hours (20%)
+- Shipping (Score 4): 6 hours (15%)
+- Promo codes (Score 4): 4 hours (10%)
+- Gift message (Score 1): 2 hours (5%)
+
+**Result:** 50% of effort on highest-risk feature (payment), proportional allocation for others.
+
+### Without Risk-Based Testing:
+
+**Equal allocation:** 8 hours per component = wasted effort on gift message, under-testing payment.
+
+**Result:** Payment bugs slip through (critical), perfect testing of gift message (trivial).
+
+## Mitigation Strategies by Risk Level
+
+### Score 9: Mandatory Mitigation (Blocks Release)
+
+```markdown
+**Gate Impact:** FAIL - Cannot deploy without mitigation
+
+**Actions:**
+- Comprehensive test suite (E2E, API, security)
+- Multiple test environments (dev, staging, prod-mirror)
+- Load testing and performance validation
+- Security audit and penetration testing
+- Monitoring and alerting
+- Rollback plan documented
+- On-call rotation assigned
+
+**Cannot deploy until score is mitigated below 9.**
+```
+
+### Score 6-8: Required Mitigation (Gate: CONCERNS)
+
+```markdown
+**Gate Impact:** CONCERNS - Can deploy with documented mitigation plan
+
+**Actions:**
+- Targeted test suite (happy path + critical errors)
+- Test environment setup
+- Monitoring plan
+- Document mitigation and owners
+
+**Can deploy with approved mitigation plan.**
+```
+
+### Score 4-5: Recommended Mitigation
+
+```markdown
+**Gate Impact:** Advisory - Does not affect gate decision
+
+**Actions:**
+- Basic test coverage
+- Standard monitoring
+- Document known limitations
+
+**Can deploy, mitigation recommended but not required.**
+```
+
+### Score 1-3: Optional Mitigation
+
+```markdown
+**Gate Impact:** None
+
+**Actions:**
+- Smoke test if desired
+- Feature flag for easy disable (optional)
+
+**Can deploy without mitigation.**
+```
+
+## Technical Implementation
+
+For detailed risk governance patterns, see the knowledge base:
+- [Knowledge Base Index - Risk & Gates](/docs/reference/tea/knowledge-base.md)
+- [TEA Command Reference - *test-design](/docs/reference/tea/commands.md#test-design)
+
+### Risk Scoring Matrix
+
+TEA uses this framework in `*test-design`:
+
+```
+           Impact
+           1    2    3
+      ┌────┬────┬────┐
+    1 │ 1  │ 2  │ 3  │ Low risk
+P   2 │ 2  │ 4  │ 6  │ Medium risk
+r   3 │ 3  │ 6  │ 9  │ High risk
+o     └────┴────┴────┘
+b      Low  Med  High
+```
+
+### Gate Decision Rules
+
+| Score | Mitigation Required | Gate Impact |
+|-------|-------------------|-------------|
+| **9** | Mandatory, blocks release | FAIL if no mitigation |
+| **6-8** | Required, documented plan | CONCERNS if incomplete |
+| **4-5** | Recommended | Advisory only |
+| **1-3** | Optional | No impact |
+
+#### Gate Decision Flow
+
+```mermaid
+%%{init: {'theme':'base', 'themeVariables': { 'fontSize':'14px'}}}%%
+flowchart TD
+    Start([Risk Assessment]) --> Score{Risk Score?}
+
+    Score -->|Score = 9| Critical[CRITICAL RISK<br/>Score: 9]
+    Score -->|Score 6-8| High[HIGH RISK<br/>Score: 6-8]
+    Score -->|Score 4-5| Medium[MEDIUM RISK<br/>Score: 4-5]
+    Score -->|Score 1-3| Low[LOW RISK<br/>Score: 1-3]
+
+    Critical --> HasMit9{Mitigation<br/>Plan?}
+    HasMit9 -->|Yes| Concerns9[CONCERNS ⚠️<br/>Can deploy with plan]
+    HasMit9 -->|No| Fail[FAIL ❌<br/>Blocks release]
+
+    High --> HasMit6{Mitigation<br/>Plan?}
+    HasMit6 -->|Yes| Pass6[PASS ✅<br/>or CONCERNS ⚠️]
+    HasMit6 -->|No| Concerns6[CONCERNS ⚠️<br/>Document plan needed]
+
+    Medium --> Advisory[Advisory Only<br/>No gate impact]
+    Low --> NoAction[No Action<br/>Proceed]
+
+    style Critical fill:#f44336,stroke:#b71c1c,stroke-width:3px,color:#fff
+    style Fail fill:#d32f2f,stroke:#b71c1c,stroke-width:3px,color:#fff
+    style High fill:#ff9800,stroke:#e65100,stroke-width:2px,color:#000
+    style Concerns9 fill:#ffc107,stroke:#f57f17,stroke-width:2px,color:#000
+    style Concerns6 fill:#ffc107,stroke:#f57f17,stroke-width:2px,color:#000
+    style Pass6 fill:#4caf50,stroke:#1b5e20,stroke-width:2px,color:#fff
+    style Medium fill:#fff9c4,stroke:#f57f17,stroke-width:1px,color:#000
+    style Low fill:#c8e6c9,stroke:#2e7d32,stroke-width:1px,color:#000
+    style Advisory fill:#e8f5e9,stroke:#2e7d32,stroke-width:1px,color:#000
+    style NoAction fill:#e8f5e9,stroke:#2e7d32,stroke-width:1px,color:#000
+```
+
+## Common Misconceptions
+
+### "Risk-based = Less Testing"
+
+**Wrong:** Risk-based testing often means MORE testing where it matters.
+
+**Example:**
+- Traditional: 50 tests spread equally
+- Risk-based: 70 tests focused on P0/P1 (more total, better allocated)
+
+### "Low Priority = Skip Testing"
+
+**Wrong:** P3 still gets smoke tests.
+
+**Correct:**
+- P3: Smoke test (feature works at all)
+- P2: Happy path (feature works correctly)
+- P1: Happy path + errors
+- P0: Comprehensive (all scenarios)
+
+### "Risk Scores Are Permanent"
+
+**Wrong:** Risk changes over time.
+
+**Correct:**
+- Initial launch: Payment is Score 9 (untested integration)
+- After 6 months: Payment is Score 6 (proven in production)
+- Re-assess risk quarterly
+
+## Related Concepts
+
+**Core TEA Concepts:**
+- [Test Quality Standards](/docs/explanation/tea/test-quality-standards.md) - Quality complements risk assessment
+- [Engagement Models](/docs/explanation/tea/engagement-models.md) - When risk-based testing matters most
+- [Knowledge Base System](/docs/explanation/tea/knowledge-base-system.md) - How risk patterns are loaded
+
+**Technical Patterns:**
+- [Fixture Architecture](/docs/explanation/tea/fixture-architecture.md) - Building risk-appropriate test infrastructure
+- [Network-First Patterns](/docs/explanation/tea/network-first-patterns.md) - Quality patterns for high-risk features
+
+**Overview:**
+- [TEA Overview](/docs/explanation/features/tea-overview.md) - Risk assessment in TEA lifecycle
+- [Testing as Engineering](/docs/explanation/philosophy/testing-as-engineering.md) - Design philosophy
+
+## Practical Guides
+
+**Workflow Guides:**
+- [How to Run Test Design](/docs/how-to/workflows/run-test-design.md) - Apply risk scoring
+- [How to Run Trace](/docs/how-to/workflows/run-trace.md) - Gate decisions based on risk
+- [How to Run NFR Assessment](/docs/how-to/workflows/run-nfr-assess.md) - NFR risk assessment
+
+**Use-Case Guides:**
+- [Running TEA for Enterprise](/docs/how-to/enterprise/use-tea-for-enterprise.md) - Enterprise risk management
+
+## Reference
+
+- [TEA Command Reference](/docs/reference/tea/commands.md) - `*test-design`, `*nfr-assess`, `*trace`
+- [Knowledge Base Index](/docs/reference/tea/knowledge-base.md) - Risk governance fragments
+- [Glossary](/docs/reference/glossary/index.md#test-architect-tea-concepts) - Risk-based testing term
+
+---
+
+Generated with [BMad Method](https://bmad-method.org) - TEA (Test Architect)