Flakey tests when testing firebase functions using Jest - node.js

Question

I'm testing Firebase functions using Jest and the emulator, though the tests are flakey presumably from a race condition. By flakey, I mean sometimes they pass and sometimes they don't, even on the same machine.
Tests and functions are written in TypeScript, then transpiled with babel.
Example test/function
Note: This is an example of just one of the flakey tests. Many other tests are flakey. A solution is preferably one that doesn't just solve this one case, but rather the general issue.
The test
import { onProfilesWrite } from '../src/profiles/on-write'
import { initializeAdminApp } from '#firebase/rules-unit-testing'
const admin = initializeAdminApp({ projectId: 'projectId' }).firestore()
const wrappedFunction = testEnvironment.wrap(onProfilesWrite)
const profilePath = `profiles/${uid}`
const customerProfile = {
roles: ['customer'],
slug: 'slug',
image: 'image.png',
fullName: 'John Smith',
}
const publisherRoles = ['customer', 'publisher']
const publisherProfile = {
...customerProfile,
roles: publisherRoles,
}
const createChange = async (
before: Record<string, unknown> | undefined,
changes: Record<string, unknown>
) => {
const publisherStatsRef = admin.doc(profilePath)
if (before) await publisherStatsRef.set(before)
const beforeSnapshot = await publisherStatsRef.get()
await publisherStatsRef.set(changes, { merge: true })
const afterSnapshot = await publisherStatsRef.get()
return testEnvironment.makeChange(beforeSnapshot, afterSnapshot)
}
test('If user profile is created as a publisher, publisherDetails is created', async () => {
const change = await createChange(undefined, publisherProfile)
await wrappedFunction(change)
const snapshot = await admin.doc(`profileDetails/${uid}`).get()
const data = snapshot.data()
expect(data).toBeTruthy()
expect(data?.id).toBeTruthy()
expect(data?.slug).toBe(publisherProfile.slug)
expect(data?.profileImage).toBe(publisherProfile.image)
expect(data?.publisherName).toBe(publisherProfile.fullName)
expect(data?.music).toMatchObject([])
})
Run the test
firebase emulators:exec \"jest functions/__tests__ --detectOpenHandles\" --only firestore
Output
If user profile is created as a publisher, publisherDetails is created
expect(received).toBeTruthy()
Received: undefined
46 | const snapshot = await admin.doc(`profileDetails/${uid}`).get()
47 | const data = snapshot.data()
> 48 | expect(data).toBeTruthy()
| ^
49 | expect(data?.id).toBeTruthy()
50 | expect(data?.slug).toBe(publisherProfile.slug)
51 | expect(data?.profileImage).toBe(publisherProfile.image)
The function
import * as functions from 'firebase-functions'
// initializes the admin app, then exports admin.firestore
import { firestore } from '../admin'
const database = firestore()
const createPublisherId = async (): Promise<string> => {
let id = ''
const MAX_NUMBER = 1000000
while (id === '') {
const temporaryId = String(Math.ceil(Math.random() * MAX_NUMBER))
const snapshot = await firestore()
.collection('publisherDetails')
.where('sku', '==', temporaryId)
.limit(1)
.get()
if (snapshot.empty) id = temporaryId
}
return id
}
export const createPublisherDetails = async (
newData: firestore.DocumentData,
uid: string
): Promise<void> => {
const id = await createPublisherId()
await database.doc(`publisherDetails/${uid}`).set(
{
id,
slug: newData.slug,
publisherName: newData.fullName,
profileImage: newData.image,
music: [],
},
{ merge: true }
)
}
export const onProfilesWrite = functions.firestore.document('profiles/{uid}').onWrite(
async (change): Promise<void> => {
const { id: uid } = change.after
const oldData = change.before.data()
const newData = change.after.data()
if (
newData?.roles?.includes('publisher') &&
(typeof oldData === 'undefined' || !oldData.roles?.includes('publisher'))
)
await createPublisherDetails(newData, uid)
}
)
Debug steps
All promises are awaited in the cloud functions (as affirmed by an ESLint rule #typescript-eslint/no-floating-promises)
Also converted the tests to Mocha (as suggested by the Firebase docs), same errors
Converting async/await in tests to promise.then() syntax
Metadata
OS: macOS 11.2, Ubuntu 18.04
Jest: 26.6.3
Firebase: 8.2.6
Firebase tools: 9.3.0
As comments roll in, with either questions or suggestions, I'll continue to update this post.

Answer 1

Change your test portion to as follows :
test('If user profile is created as a publisher, publisherDetails is created', async () => {
const change = await createChange(undefined, publisherProfile)
await wrappedFunction(change)
const documentObject = await admin.doc(`profileDetails/${uid}`)
const snapshot = await documentObject.get()
const data = snapshot.data()
expect(data).toBeTruthy()
expect(data?.id).toBeTruthy()
expect(data?.slug).toBe(publisherProfile.slug)
expect(data?.profileImage).toBe(publisherProfile.image)
expect(data?.publisherName).toBe(publisherProfile.fullName)
expect(data?.music).toMatchObject([])
})
Reason being that in your test region, your use of await is a bit incorrect (function chaining on an object that is being waited for is a big no-no in the same calling line)