Qfyilyi

I am trying to test mysqlite3 data access layer but I can't seem to correctly stub my db.all() method, I am unsure if this is due to how my database is passed in or whether I am stubbing it wrong.

This is my database file:

const db = new sqlite3.Database(path.join(__dirname, ' 

../database/example.db'), (err) => {

    if (err) return console.log(err.message)

    console.log('Connected to the database')

})



module.exports.database = db

This is my function I am trying to stub:

const db = require('./database.js').database



module.exports.selectMultiple = request => {

    //unimportant code

    return new Promise((resolve, reject) => {

        db.all(sql, (err, rows) => {

            if (err)

                reject(err)

            else {

                resolve('blah blah blah')

        })

    })

}

This is my attempt which I can't seem to get working:

const db = require('../../data_access/database.js').database



describe('select multiple', () => {

    beforeEach(() => {

        const testProduct2 = JSON.parse(JSON.stringify(testProduct))

        testProduct2['key'] = '2'

        this.multiple = sinon.stub(db, 'all')

            .resolves([testProduct, testProduct2])

    })



    afterEach(() => {

        this.multiple.restore()

    })



    test('select 2 products', async(done) => {

        expect.assertions(2)

        const macbooks = await productDb.selectMultiple({amount: 2})

        expect(macbooks.length === 2).toBe(true)

        expect(macbooks[0].key !== macbooks[1].key).toBe(true)

        done()

    })

})

If I run this the async test block times out. Does anyone know how I should be stubbing this?

Thanks!

Issue

db.all does not return a Promise, it uses a callback as the second argument.

stub.resolves causes the stub to return a Promise so the callback is never called and the Promise returned by selectMultiple never resolves causing the test to timeout on await productDb.selectMultiple({ amount: 2 }).

Solution

Stub db.all using stub.callsArgWith so that the callback passed as the second argument is called:

describe('select multiple', () => {

  beforeEach(() => {

    const testProduct2 = JSON.parse(JSON.stringify(testProduct))

    testProduct2['key'] = '2'

    this.multiple = sinon.stub(db, 'all')

      .callsArgWith(1, null, [testProduct, testProduct2]);  // use stub.callsArgWith

  })



  afterEach(() => {

    this.multiple.restore()

  })



  test('select 2 products', async () => {

    expect.assertions(2)

    const macbooks = await productDb.selectMultiple({ amount: 2 })

    expect(macbooks.length === 2).toBe(true)  // SUCCESS

    expect(macbooks[0].key !== macbooks[1].key).toBe(true)  // SUCCESS

  })

})

Also note that you don't need to use done since you are using an async test function and are using await on the call to productDb.selectMultiple.