Multi tool use

Catch on JS Promise being called but not calling other jest mocked object

I have a simple js function that tries to connect to mongodb via a Promise and either succeeds of fails.

const MongodbService = () => {
mongoose.connect(mongodbUrl, options).then(() => {
logger.info('Mongodb Connected', { url: process.env.MONGODB_URL })
}).catch(err => {
logger.error('Mongodb: ${err}', { url: process.env.MONGODB_URL })
})

return mongoose
}


and I want to simply test it. I mock the logger:

import logger from '../../../config/winston'
jest.mock('../../../config/winston')


I have spec for testing success, which works as expected:

it('it should handle a connection success', async () => {
mongoose.connect = jest.fn(() => Promise.resolve())
await MongodbService()
expect(logger.info.mock.calls[0][0]).toEqual('Mongodb Connected')
expect(logger.info.mock.calls[0][1]).toEqual({ url: 'mongodb://mongodb/jb-dev' })
})


I have another which check for failure, and this is where I'm stuck:

it('it should handle a connection failure', async () => {
mongoose.connect = jest.fn(() => Promise.reject(new Error('boom')))
await MongodbService()
expect(logger.error.mock.calls[0][0]).toEqual('Mongodb Error: boom')
})


This is failing stating the logger has not been called, even though when I put a console.log in the function I can see it has correctly been called. If I add a setTimeout around the expect I can then see the logger being called, but it's been called twice. I think I'm missing something simple. Can anyone point me in the right direction?

1 Answer
1

Doh! So I was miss-understanding the information returned when I thought it was not working. Adding nextTick worked for me just fine:

it('it should handle a connection failure', async () => {
mongoose.connect = jest.fn(() => Promise.reject(new Error('bang')))
await MongodbService()
process.nextTick(() => {
expect(logger.error.mock.calls[0][0]).toEqual('Mongodb: Error: bang')
})
})


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