Unit Testing newRelic.increment Metric

Question

I have a controller that calls newrelic.incrementMetric() and I want to write an assert that checks that its called with the properly

my controller looks like

const newrelic = require('newrelic')

async index() {
  // some stuff here
  newrelic.incrementMetric('hello', 1)
}

I tried this in my test

const newrelic = require('newrelic')

// describe block here...
  it('should call newRelic', async () => {
    newrelic.incremetentMetric = jest.fn().mockResolvedValueOnce({});
    expect (newrelic.incrementMetric).toHaveBeenCalledWith('hello', 1)
  });

Whats the proper way to do this?

My code has an error

    Matcher error: received value must be a mock or spy function

    Received has type:  function
    Received has value: [Function incrementMetric]
    ```

Answer 1

Using jest.mock factory to mock newrelic. In the test case you have to call controller's function (A - action).

index.ts

import newrelic from 'newrelic'

class Controller {
  index() {
    // some stuff here
    newrelic.incrementMetric('hello', 1)
  }
}

export default new Controller()

index.spec.ts

import newrelic from 'newrelic'
import controller from './index'

jest.mock('newrelic', () => {
  return {
    incrementMetric: jest.fn(),
  }
})

describe('Controller', () => {
  it('should call incrementMetric with correct', () => {
    controller.index()

    expect(newrelic.incrementMetric).toHaveBeenCalledWith('hello', 1)
  })
})