Sinon/sandbox test says that function was never called - node.js

Question

I want to write a unit test that checks to see if a function was called, but i'm getting the error:
submitDetails
submitDetails
sendEmail:
AssertionError: expected sendEmail to have been called exactly once, but it was called 0 times
From what I can see my function submitDetails.submitDetails clearly runs the function sendEmail.sendEmail but it's saying that it's never called. I've also tried just using 'spy.called' instead of calledOnce but I get the same result.
Test file:
const submitDetails = require('../src/scripts/submitDetails')
const sendEmail = require('../src/lib/sendEmail')
describe('submitDetails', function () {
let sandbox = null
before(() => {
sandbox = sinon.createSandbox()
})
afterEach(() => {
sandbox.restore()
})
describe('submitDetails', () => {
let mockParams, result
beforeEach(async () => {
sandbox.spy(sendEmail, 'sendEmail')
})
it('sendEmail', () => {
expect(sendEmail.sendEmail).to.have.been.calledOnce()
})
})
})
SubmitDetails.js (file that's being test)
const { sendEmail } = require('../lib/sendEmail')
const submitDetails = {}
submitDetails.submitDetails = query => {
return sendEmail(query)
}
module.exports = submitDetails

Answer 1

You didn't call submitDetails.submitDetails() method in your test case. Here is the working example:
sendEmail.ts:
module.exports = {
sendEmail() {}
};
submitDetails.ts:
const sendEmail = require('./sendEmail');
// #ts-ignore
const submitDetails = {};
// #ts-ignore
submitDetails.submitDetails = query => {
return sendEmail.sendEmail(query);
};
module.exports = submitDetails;
submitDetails.spec.ts:
import { expect } from 'chai';
import sinon, { SinonSandbox, SinonSpy } from 'sinon';
const submitDetails = require('./submitDetails');
const sendEmail = require('./sendEmail');
describe('submitDetails', () => {
let sandbox: SinonSandbox;
before(() => {
sandbox = sinon.createSandbox();
});
afterEach(() => {
sandbox.restore();
});
describe('submitDetails', () => {
let sendEmailSpy: SinonSpy;
beforeEach(() => {
sendEmailSpy = sandbox.spy(sendEmail, 'sendEmail');
});
it('sendEmail', () => {
submitDetails.submitDetails();
sandbox.assert.calledOnce(sendEmailSpy);
expect(sendEmailSpy.calledOnce).to.be.true;
});
});
});
Unit test result:
submitDetails
submitDetails
✓ sendEmail
1 passing (22ms)
Source code: https://github.com/mrdulin/mocha-chai-sinon-codelab/tree/master/src/stackoverflow/58058653