Testing Moleculer services with event interfaces

package.json

{
  "name": "moleculer-event-testing",
  "version": "0.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "jest --watch some-process.service.spec.js"
  },
  "keywords": [],
  "author": "Sid Wood",
  "license": "UNLICENSED",
  "dependencies": {
    "moleculer": "^0.13.5"
  },
  "devDependencies": {
    "jest": "^23.6.0"
  }
}

some-process.service.js

'use strict'

module.exports = {
  name: 'some-process',
  events: {
    'process.start'(graph) {
      return this.doWork(graph)
    }
  },
  methods: {
    doWork(graph) {
      return this.broker.Promise
        .resolve({some: 'value'})
        .then((entity) => {
          graph.entities.push(entity)
          this.broker.emit('process.complete', graph)
        })
        .catch((err) => {
          this.logger.error(err)
        })
    }
  }
}

some-process.service.spec.js

'use strict'

// 3rd-party
const {ServiceBroker} = require('moleculer')

// sut
const serviceSchema = require('./index')

// init
const broker = new ServiceBroker({logLevel: 'error'})
const given = describe
const spy = jest.fn()

describe('some-process.service', () => {
  beforeAll(() => {
    serviceSchema.events['process.complete'] = spy
    this.service = broker.createService(serviceSchema)
    return broker.start()
  })

  afterAll(async () => {
    await broker.destroyService(this.service)
    await broker.stop()
  })

  given('"process.start" event', () => {
    it('processes the event as expected', () => {
      broker.emit('process.start', getInputGraph())
      return broker.Promise.delay(100).then(() => {
        expect(spy).toHaveBeenCalledWith(
          getOutputGraph(),
          broker.nodeID,
          'process.complete'
        )
      })
    })
  })
})

function getInputGraph() {
  return {
    entities: []
  }
}

function getOutputGraph() {
  return {
    entities: [{some: 'value'}]
  }
}