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Testing Overview

Strategies for testing saga-based applications.

Testing Levels​

Test Harness​

The @saga-bus/test package provides utilities:

npm install -D @saga-bus/test
import { TestHarness } from '@saga-bus/test';

const harness = new TestHarness();
await harness.start({ sagas: [{ definition: orderSaga }] });

await harness.publish({ type: 'OrderSubmitted', orderId: '123', ... });
await harness.waitForSaga('OrderSaga', '123');

const state = await harness.getSagaState('OrderSaga', '123');
expect(state.status).toBe('pending');

Quick Examples​

Unit Test​

import { describe, it, expect } from 'vitest';

describe('Order handler', () => {
  it('transitions to paid on PaymentCaptured', async () => {
    const state = { orderId: '123', status: 'pending' };
    const msg = { type: 'PaymentCaptured', transactionId: 'txn' };

    const newState = await orderSaga.handlers.PaymentCaptured(msg, state, mockCtx);

    expect(newState.status).toBe('paid');
  });
});

Integration Test​

describe('Order flow', () => {
  it('completes order', async () => {
    const harness = new TestHarness();
    await harness.start({ sagas: [{ definition: orderSaga }] });

    await harness.publish({ type: 'OrderSubmitted', orderId: '123' });
    await harness.publish({ type: 'PaymentCaptured', orderId: '123' });
    await harness.publish({ type: 'InventoryReserved', orderId: '123' });

    const state = await harness.getSagaState('OrderSaga', '123');
    expect(state.status).toBe('completed');
  });
});

Sections​