Native Test Runner: Error to mocking "find" method from "db.addCollection('schedule')" of LokiJS (1.15.12)

[vitorvd]

Details

I'm trying to get 100% of coverage in my code and I have to test the repository layer, so: I have a file called todoRepository.js:

export default class TodoRepository {
    #schedule
    constructor({ db }) { //db is an instance from LokiJS
        this.#schedule = db.addCollection('schedule')
        console.log('schedule', this.#schedule)
    }

    async list() {
        return this.#schedule.find().map(({ meta, $loki, ...result }) => result)
    }

    async create(data) {
        const { $loki, meta, ...result} = this.#schedule.insertOne(data)
        return result
    }
}

And I have my test called todoRepository.test.js:

import { describe, it, beforeEach, afterEach } from 'node:test'
import TodoRepository from '../src/todoRepository.js'
import assert from 'node:assert'
import sinon from 'sinon'

describe('todoRepository test Suite', () => {
  describe('#list', () => {
    let _todoRepository
    let _dependencies
    let addCollectionStub

    const mockDatabase = [
      {
        text: 'I must plan my trip to Europe',
        when: new Date('2021-03-22T00:00:00.000Z'),
        status: 'late',
        id: '31f1825e-c8e3-4098-ae8b-47b1da426442',
        meta: { revision: 0, created: 1693765894381, version: 0 },
        '$loki': 3
      }
    ]

    beforeEach((context) => {
      _dependencies = {
        db: {
          addCollection: addCollectionStub = sinon.stub(),
          find: context.mock.fn(async () => mockDatabase)
        }
      }
      _todoRepository = new TodoRepository(_dependencies)
    })

    afterEach(() => {
      addCollectionStub.restore();
    })

    it('should return a list of items', async () => {
      const expected = [
        {
          text: 'I must plan my trip to Europe',
          when: new Date('2021-03-22T00:00:00.000Z'),
          status: 'late',
          id: '31f1825e-c8e3-4098-ae8b-47b1da426442'
        }
      ]

      const result = await _todoRepository.list()
      assert.deepStrictEqual(result, expected)

    })

  })
})

But when I tried run my tests, I got this error:

todoRepository test Suite
  ▶ #list
    ✖ should return a list of items (4.074102ms)
      TypeError [Error]: Cannot read properties of undefined (reading 'find')
          at TodoRepository.list (file:///home/vitor.duda/Desktop/estudos/mocking-with-node-test-runner-template/src/todoRepository.js:9:31)
          at TestContext.<anonymous> (file:///home/vitor.duda/Desktop/estudos/mocking-with-node-test-runner-template/test/todoRepository.test.js:47:44)
          at Test.runInAsyncScope (node:async_hooks:206:9)
          at Test.run (node:internal/test_runner/test:580:25)
          at async Promise.all (index 0)
          at async Suite.run (node:internal/test_runner/test:824:7)
          at async Promise.all (index 0)
          at async Suite.run (node:internal/test_runner/test:824:7)
          at async startSubtest (node:internal/test_runner/harness:204:3)

But I didn't understand it because I'm mocking the return value from find with:

find: context.mock.fn(async () => mockDatabase)

The line db.addCollection('schedule') returns a class LokiEventEmitter, such as:

LokiEventEmitter {
  name: 'schedule',
  data: [],
  idIndex: null,
  binaryIndices: {},
  constraints: { unique: {}, exact: {} },
  uniqueNames: [],
  transforms: {},
  objType: 'schedule',
  dirty: true,
  cachedIndex: null,
  cachedBinaryIndex: null,
  cachedData: null,
  adaptiveBinaryIndices: true,
  transactional: false,
  cloneObjects: false,
  cloneMethod: 'parse-stringify',
  asyncListeners: false,
  disableMeta: false,
  disableChangesApi: true,
  disableDeltaChangesApi: true,
  autoupdate: false,
  serializableIndices: true,
  disableFreeze: true,
  ttl: { age: null, ttlInterval: null, daemon: null },
  maxId: 0,
  DynamicViews: [],
  events: {
    insert: [],
    update: [],
    'pre-insert': [],
    'pre-update': [],
    close: [],
    flushbuffer: [],
    error: [],
    delete: [ [Function: deleteCallback] ],
    warning: [ [Function (anonymous)] ]
  },
  changes: [],
  dirtyIds: [],
  observerCallback: [Function: observerCallback],
  getChangeDelta: [Function: getChangeDelta],
  getObjectDelta: [Function: getObjectDelta],
  getChanges: [Function (anonymous)],
  flushChanges: [Function: flushChanges],
  setChangesApi: [Function (anonymous)],
  isIncremental: undefined
}

I believe that I'm getting this error due to method find is outside from addCollection. I think I have to create of a mock from LokiEventEmitter class with the find method, but I don't know how to do it.

Node.js version

20.5.1

Example code

No response

Operating system

Linux 6.2.0-31-generic #31~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Wed Aug 16 13:45:26 UTC 2 x86_64 x86_64 x86_64 GNU/Linux

Scope

Running tests with native test runner

Module and version

Not applicable.

[preveen-stack]

Not able to understand the reason for the error. https://www.sammeechward.com/mocking-a-database-with-jest-in-javascript

[github-actions[bot]]

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[github-actions[bot]]

It seems there has been no activity on this issue for a while, and it is being closed. If you believe this issue should remain open, please leave a comment. If you need further assistance or have questions, you can also search for similar issues on Stack Overflow. Make sure to look at the README file for the most updated links.