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Testing with SyntropyLog

Use the syntropylog/testing entry point for mocks and helpers. No framework initialization or shutdown in tests; no Redis, HTTP, or broker in the core package.

What the package provides​

From syntropylog/testing:

  • createTestHelper(spyFn?) — Returns { mockSyntropyLog, beforeEach, afterEach }. Use mockSyntropyLog in place of the real syntropyLog in tests.
  • createSyntropyLogMock(spyFn?) — Creates a mock framework instance (getLogger, getContextManager, etc.).
  • createServiceWithMock(ServiceClass, mockSyntropyLog) — Instantiates a service with the mock injected.
  • SpyTransport — Transport that captures log entries in memory for assertions.
  • MockContextManager — In-memory context manager for tests.

The core package does not include Redis, HTTP, or broker mocks. Use your own mocks or stubs for those.

No init in tests (zero boilerplate for tests)​

No init/shutdown in tests:

import { createTestHelper } from 'syntropylog/testing';

const testHelper = createTestHelper(vi.fn); // or jest.fn

describe('UserService', () => {
  beforeEach(() => testHelper.beforeEach());

  it('should create user', async () => {
    const service = createServiceWithMock(UserService, testHelper.mockSyntropyLog);
    const result = await service.createUser({ name: 'John' });
    expect(result).toHaveProperty('userId');
  });
});

Spy function injection​

Pass your test framework’s spy so mocks behave consistently:

// Vitest
const testHelper = createTestHelper(vi.fn);

// Jest
const testHelper = createTestHelper(jest.fn);

Capturing logs with SpyTransport​

Use SpyTransport to assert on log output:

import { SpyTransport, createSyntropyLogMock } from 'syntropylog/testing';

const spyTransport = new SpyTransport();
const mock = createSyntropyLogMock();
// Attach spyTransport to the mock logger as needed for your test setup
// Then assert:
// expect(spyTransport.getEntries()).toContainEqual(expect.objectContaining({ level: 'info', message: '...' }));

Runnable examples (syntropylog-examples)​

Testing examples 13–16 in the repo:

  • 13-testing-patterns — Vitest
  • 14-testing-patterns-jest — Jest
  • 15-testing-serializers — Serializers
  • 16-testing-transports-concepts — Transport concepts

See the Examples page for the full list (00–17).

Testing guides in this site​

Best practices​

  • Use createTestHelper() or createSyntropyLogMock() so tests don’t depend on real init/shutdown.
  • Test behavior and outcomes, not framework internals.
  • Use SpyTransport when you need to assert on log entries.
  • Keep production and testing imports separate: syntropylog for app code, syntropylog/testing for tests.