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 90% coverage.

When to Use

• Writing unit tests for new or modified code
• Fixing failing tests after code changes
• Maintaining 90% code coverage
• Fixing SonarQube issues or code smells

Coverage Requirements

• Statements: 90%
• Branches: 90%
• Functions: 90%
• Lines: 90%
• 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 — 90% coverage required
4. Write tests for every code path including error branches
5. Run npm test and verify 90% coverage across all metrics
6. If any metric is below 90%, identify uncovered lines and add tests
7. Check problems tab for SonarQube issues