Testing Strategy

Systematic test planning and coverage improvement workflow.

When to Use

Trigger	Description
Post-COMPLEX Feature	After implementing major features
Coverage Drop	When coverage falls below thresholds
Test Debt Sprint	Dedicated testing improvement effort
New Project	Establishing testing foundation
Pre-Release	Ensuring quality before deployment

Coverage Targets

Category	Target	Warning	Critical
Business Logic	>80%	70-80%	<70%
Overall	>60%	50-60%	<50%
Critical Paths	>90%	80-90%	<80%

Prerequisites

Before starting:

Test framework configured
Coverage tool available
CI/CD running tests
Access to current coverage report
Understanding of business-critical features

Strategy Process

Phase 1: Coverage Analysis
    ↓
Phase 2: Critical Path Identification
    ↓
Phase 3: Test Pyramid Planning
    ↓
Phase 4: Test Prioritization
    ↓
Phase 5: Edge Case Planning
    ↓
Phase 6: Flaky Test Remediation
    ↓
Phase 7: Implementation Roadmap

Phase 1: Coverage Analysis

1.1 Generate Coverage Report

Node.js (Jest/Vitest):

npm test -- --coverage
# or
npx vitest run --coverage

Python (pytest):

pytest --cov=src --cov-report=html

Go:

go test -cover ./...
go test -coverprofile=coverage.out ./...
go tool cover -html=coverage.out

Rust:

cargo tarpaulin --out Html

1.2 Analyze Coverage Gaps

Review coverage report for:

Area	Target	Current	Gap
`src/auth/`	90%	45%	-45%
`src/api/`	80%	62%	-18%
`src/utils/`	60%	78%	+18%
Overall	60%	55%	-5%

1.3 Identify Uncovered Files

List files with lowest coverage:

Lowest Coverage Files:
1. src/auth/oauth.ts - 12% (critical!)
2. src/api/payments.ts - 28% (critical!)
3. src/services/email.ts - 35%
4. src/utils/validation.ts - 42%
5. src/api/users.ts - 48%

Phase 2: Critical Path Identification

2.1 Define Critical Paths

Critical paths are user journeys that MUST work:

Path	Description	Files	Priority
Authentication	Login, logout, session	auth/*	P0
Checkout	Cart → Payment → Confirm	payments/, cart/	P0
Registration	Signup → Verify → Profile	users/, email/	P1
Search	Query → Results → Filter	search/, api/	P1

2.2 Map Critical Files

For each critical path, list involved files:

Authentication Path:

src/auth/login.ts        - 45% coverage
src/auth/session.ts      - 52% coverage
src/auth/middleware.ts   - 88% coverage
src/models/user.ts       - 72% coverage

2.3 Calculate Critical Path Coverage

Authentication Path:
- Total lines: 450
- Covered lines: 267
- Coverage: 59% (target: 90%)
- Gap: 183 lines to cover

Phase 3: Test Pyramid Planning

3.1 Ideal Test Pyramid

         /\
        /  \
       / E2E \         10% - Slow, expensive, covers user flows
      /______\
     /        \
    /Integration\      20% - Medium speed, covers integrations
   /______________\
  /                \
 /    Unit Tests    \  70% - Fast, cheap, covers logic
/____________________\

3.2 Current Distribution

Analyze current test distribution:

Current State:
- Unit tests: 45 (60%)
- Integration: 25 (33%)
- E2E: 5 (7%)

Ideal State:
- Unit tests: 70 (70%)
- Integration: 20 (20%)
- E2E: 10 (10%)

Gap:
- Need +25 unit tests
- Need -5 integration tests (or OK)
- Need +5 E2E tests

3.3 Test Type Guidelines

Unit Tests (70%):

Pure functions
Business logic
Utility functions
Model methods
State transitions

Integration Tests (20%):

API endpoints
Database operations
Service interactions
Authentication flows
External service mocks

E2E Tests (10%):

Critical user journeys
Happy path scenarios
Cross-system flows
Smoke tests

Phase 4: Test Prioritization

4.1 Priority Matrix

Priority	Criteria	Example
P0	Critical path, no tests	Payment processing
P1	Critical path, low coverage	Authentication
P2	High risk, medium coverage	Data validation
P3	Medium risk, any coverage	Utility functions
P4	Low risk, nice to have	Formatting helpers

4.2 Effort Estimation

Test Type	Effort	Coverage Impact
Unit (simple)	15 min	High
Unit (complex)	1 hour	High
Integration	2 hours	Medium
E2E	4 hours	Low (but valuable)

4.3 Prioritized Test Backlog

## Test Backlog

### P0 - Immediate (This Sprint)
- [ ] Unit: payment.processPayment()
- [ ] Unit: auth.validateToken()
- [ ] Integration: POST /api/payments
- [ ] E2E: Complete checkout flow

### P1 - High (Next Sprint)
- [ ] Unit: auth.refreshToken()
- [ ] Unit: user.validateEmail()
- [ ] Integration: GET /api/users/:id
- [ ] E2E: Registration flow

### P2 - Medium (Backlog)
- [ ] Unit: validation helpers
- [ ] Unit: formatting utilities
- [ ] Integration: Search API

### P3 - Low (Nice to Have)
- [ ] Unit: logging utilities
- [ ] Unit: config loaders

Phase 5: Edge Case Planning

5.1 Required Edge Cases

Every function should test:

Category	Cases	Example
Null/Undefined	null, undefined input	`validateUser(null)`
Empty	"", [], {}	`searchUsers("")`
Boundary	0, -1, MAX_INT	`setQuantity(0)`
Invalid Type	Wrong type input	`calculatePrice("abc")`
Concurrent	Race conditions	Parallel updates

5.2 Edge Case Checklist

For each function:

Phase 6: Flaky Test Remediation

6.1 Identify Flaky Tests

Signs of flaky tests:

Intermittent failures in CI
Tests that pass locally but fail in CI
Tests that depend on execution order
Tests with timing-dependent assertions

6.2 Common Causes & Fixes

Cause	Symptom	Fix
Timing	Random timeouts	Use proper async/await
Order dependency	Fails when run alone	Reset state in beforeEach
Shared state	Random failures	Isolate test data
External services	Network failures	Mock external calls
Date/time	Fails at midnight	Mock dates

Phase 7: Implementation Roadmap

7.1 Sprint Planning Template

## Sprint 1: Critical Path (2 weeks)

### Goals
- Achieve 90% coverage on authentication
- Achieve 90% coverage on payments
- Add 5 E2E tests for critical paths

### Tasks
1. Unit tests for auth module (20 tests)
2. Unit tests for payment module (15 tests)
3. Integration tests for auth API (5 tests)
4. E2E test: Complete checkout (1 test)
5. E2E test: Login flow (1 test)

### Expected Outcome
- Overall coverage: 55% → 65%
- Critical path coverage: 59% → 90%

7.2 Test Writing Guidelines

Test Structure:

describe('Module or Function', () => {
  // Setup
  beforeEach(() => {
    // Reset state
  });

  describe('method or scenario', () => {
    it('should [expected behavior] when [condition]', () => {
      // Arrange
      const input = createTestInput();

      // Act
      const result = functionUnderTest(input);

      // Assert
      expect(result).toEqual(expectedOutput);
    });
  });
});

Naming Convention:

should [expected behavior] when [condition]

Examples:
- should return user when valid ID provided
- should throw error when user not found
- should update timestamp when saving

7.3 Coverage Tracking

Track coverage weekly:

Week	Overall	Business	Critical	Tests Added
1	55%	62%	59%	+15
2	62%	75%	78%	+22
3	68%	82%	88%	+18
4	72%	85%	92%	+12

Quick Reference

Coverage Commands

# Node.js
npm test -- --coverage --coverageReporters=text-summary

# Python
pytest --cov=src --cov-report=term-missing

# Go
go test -cover ./... | grep -E "coverage:"

# Rust
cargo tarpaulin --out Stdout

Test Templates

Unit Test:

describe('functionName', () => {
  it('should [behavior] when [condition]', () => {
    const result = functionName(input);
    expect(result).toEqual(expected);
  });
});

Integration Test:

describe('POST /api/resource', () => {
  it('should create resource when valid data', async () => {
    const response = await request(app)
      .post('/api/resource')
      .send(validData);
    expect(response.status).toBe(201);
  });
});

Checklist

Analysis

Coverage report generated
Gaps identified
Critical paths mapped
Current pyramid analyzed

Planning

Tests prioritized
Edge cases documented
Flaky tests identified
Sprint plan created

Implementation

P0 tests written
P1 tests written
Edge cases covered
Flaky tests fixed

Validation

Coverage targets met
All tests passing
No flaky tests
CI/CD updated

Extended Resources

For detailed examples, patterns, and in-depth guidance, see:

references/process.md - Comprehensive testing patterns and examples

Related Resources

code-review - Includes test validation
refactoring - Tests enable safe refactoring
troubleshooting - When tests fail unexpectedly

testing-strategy