unit-tests

Shared Reference Data — Unit Tests Skill

Expert in writing and maintaining unit tests for the MMO Shared Reference Data library. This shared library enforces tiered coverage targets.

When to Use

• Writing unit tests for new or modified code
• Fixing failing tests after code changes
• Maintaining the tiered coverage targets below
• Fixing SonarQube issues or code smells

Coverage Requirements

Tiered targets (aligned with copilot-instructions quality gates) — never drop below the SonarCloud baseline:

• ≥90% global — Statements, Functions, Lines, Branches
• ≥95% — core business logic (query functions, transformations, risk scoring, weight/overuse validation)
• 100% — error-handling and security-critical paths (OAuth2/API failures, Service Bus publish failures, input/date validation)
• Run tests: npm test (single run with coverage report)
• Watch mode: npm run test:watch

Test Framework & Tools

• Jest as test runner with ts-jest
• sinon for stubs and spies
• Test files in test/ directory mirroring src/ structure

Mocking Patterns

Boomi/CEFAS API (OAuth2)

// Mock both success and dual error handling
jest.mock('axios');
const mockedAxios = axios as jest.Mocked<typeof axios>;

// Success
mockedAxios.post.mockResolvedValueOnce({ data: { access_token: 'token' } });
mockedAxios.get.mockResolvedValueOnce({ data: mockApiData });

// Error with response (HTTP error)
mockedAxios.get.mockRejectedValueOnce({
  response: { status: 500, data: 'Server Error' },
});

// Error without response (network error)
mockedAxios.get.mockRejectedValueOnce(new Error('ECONNREFUSED'));

Azure Service Bus (Class-Based Mock)

// Class-based mocks for Service Bus client
const mockSender = {
  sendMessages: jest.fn().mockResolvedValue(undefined),
  close: jest.fn().mockResolvedValue(undefined),
};
const mockSbClient = {
  createSender: jest.fn().mockReturnValue(mockSender),
  close: jest.fn().mockResolvedValue(undefined),
};
jest.mock('@azure/service-bus', () => ({
  ServiceBusClient: jest.fn().mockImplementation(() => mockSbClient),
}));

Filesystem Fallback (Queue Dev Mode)

jest.mock('fs/promises', () => ({
  writeFile: jest.fn().mockResolvedValue(undefined),
  mkdir: jest.fn().mockResolvedValue(undefined),
}));

Date Mocking for CEFAS

// CEFAS requires UTC dates in YYYY-MM-DD format
jest.spyOn(Date, 'now').mockImplementation(() => 1693751375000);
// Verify: moment.utc().format('YYYY-MM-DD') === '2023-09-03'

What to Test

1. Barrel exports — verify all public API is exported from src/index.ts
2. Boomi OAuth2 — token fetch, API call with bearer, dual error handling (e.response + direct)
3. Service Bus — send with sessionId, sender/client cleanup in finally, filesystem fallback
4. Weight validation — overuse with 10% tolerance (estimated) and fixed buffer (actual), boundary values
5. AJV validation — valid/invalid payloads, schema error reporting
6. Type interfaces — ensure type guards match interface definitions
7. Legacy SSL — SSL_OP_LEGACY_SERVER_CONNECT option set on HTTPS agent
8. Date formatting — moment.utc() produces correct YYYY-MM-DD for CEFAS
9. Logging — bracketed format with Bunyan

SonarQube Issue Resolution

When fixing SonarQube issues, NEVER modify functionality. If existing tests fail after a fix, revert it. Only structural refactoring is allowed.

Workflow

1. Identify the source file(s) that need tests
2. Find existing test file or create new one mirroring src/ → test/ path
3. Read the source code to understand ALL branches — cover every path to meet the tiered targets
4. Write tests for every code path including error branches (error-handling/security paths need 100%)
5. Run npm test and verify coverage meets the tiered targets across all metrics
6. If any metric is below target, identify uncovered lines and add tests
7. Check problems tab for SonarQube issues