CODEWITHSUNDEEP
javascriptnode.jsmocha.js
Catfish
Catfish

Reputation: 19284

How to mock an object with a function that has a callback?

I have this simple method that i'm trying to test.

function isS3Healthy(s3, logger = console) {
  return new Promise((resolve, reject) => {
    s3.listObjects({}, (err, data) => {
      if (err) {
        logger.error(err)
        return resolve(['s3', false])
      }
      return resolve(['s3', true])
    })
  })
}

My test keeps timing out and it has to do with my mocked object isn't right. What does this mock object need to look like in order to test my method properly?

describe.only('#isS3Healthy', () => {
  let s3
  before(() => {
    s3 = {
      listObjects: ({}, (err, data) => {
        return Promise.resolve(['s3', true])
      })
    }
  })

  it('should return that it is healthy', () => {
    return isS3Healthy(s3)
      .then(result => {
        const [name, status] = result
        expect(name).to.equal('s3')
        expect(status).to.be.true
      })
      .catch(err => {
        console.log('err = ', err)
      })
  })
})

Upvotes: 0

Views: 212

Answers (1)

JLRishe
JLRishe

Reputation: 101652

Based on the code you've provided, it looks like listObjects is a function that accepts an object and a callback, and at some point calls that callback, so probably the simplest way to mock it would be like this:

listObjects: (_, c) => c()

The function you're testing only seems to care whether listObjects is passing an error to the callback or not, so this should seemingly be sufficient.

Side note: you have return resolve in two places in your isS3Healthy function, but using return here almost certainly serves no purpose. To resolve a promise, just call resolve(...) without returning it.

Upvotes: 1

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