Correct way to use done() while testing asyc/await with mocha

Question

I am practicing basic unit test cases with mocha and a bit confused HOW and WHEN to use done() handler.

Answer 1

The correct way is to not use done with async..await. Mocha supports promises and is able to chain a promise that is returned from it, etc. functions. And async function is syntactic sugar for a function that always returns a promise:

it('Testing insertDocumentWithIndex', async () => {
    var data = await db.insertDocumentWithIndex('inspections', {
      "inspectorId" : 1,
      "curStatus" : 1,
      "lastUpdatedTS" : 1535222623216,
      "entryTS" : 1535222623216,
      "venueTypeId" : 1,
      "location" : [
        45.5891279,
        -45.0446183
      ]
    })
    expect(data.result.n).to.equal(1);
    expect(data.result.ok).to.equal(1);
})

done is needed only for testing asynchronous APIs than don't involve promises. Even then, converting to promises often results in cleaner control flow.

And this

it('Testing insertDocumentWithIndex', async () => {
  return new Promise(async (resolve, reject) => {
  ...

is promise construction antipattern, which is even worse because of async promise constructor callback.

These concerns also apply to other JS testing frameworks with similar API, Jest and Jasmine.