Error when unit testing cloud function: no document found to update - firebase

Question

I am following the firebase documentation for unit testing. I created a simple cloud function that is triggered when a firestore document is created. It turns the value in that document to uppercase. I tried the function by creating a document and it worked as expected.
I use jest for the test. When I run the test I get the following error:
NOT_FOUND: No document to update: projects/myproject/databases/(default)/documents/test/testId
10 | return admin.firestore().doc(`test/` + snap.id)
> 11 | .update({ input: input });
| ^
12 | });
I added a console.log to my function to see what data was passed by the unit-test. It passes the right data (meaning the right document id and the right value for "input".
I'm not sure what I'm missing here. It's a simple function and a simple test. I don't understand how the function could receive the right data but not found the document, or how the document is not created in firestore when the test is run.
The function:
import * as functions from 'firebase-functions';
import * as admin from 'firebase-admin';
export const makeUpperCase = functions.firestore
.document('test/{id}')
.onCreate((snap, context) => {
const data = snap.data();
const input = data.input.toUpperCase();
console.log('new data: ' + input + ', id: ' + snap.id);
return admin.firestore().doc('test/' + snap.id)
.update({ input: input });
});
index.ts:
import * as admin from 'firebase-admin';
admin.initializeApp();
export { makeUpperCase } from './makeUpperCase';
the test (basicTest.test.ts):
import * as functions from 'firebase-functions-test';
import * as admin from 'firebase-admin';
import 'jest';
const testEnv = functions({
databaseURL: "https://mydb.firebaseio.com",
projectId: "myproject",
}, './service-account.json');
testEnv.mockConfig({});
import { makeUpperCase } from '../src/index';
describe('basicTest', () => {
let wrapped: any;
beforeAll(() => {
wrapped = testEnv.wrap(makeUpperCase);
});
test('converts input to upper case', async () => {
const path = 'test/testId';
const data = { input: 'a simple test' };
const snap = await testEnv.firestore.makeDocumentSnapshot(data, path);
await wrapped(snap);
const after = await admin.firestore().doc(path).get();
expect(after.data()!.input).toBe('A SIMPLE TEST');
});
});

Answer 1

The problem comes from your use of the import syntax. Unlike require, the import instructions are performed asynchronously before the script that is importing them is executed.
import * as module1 from 'module1';
console.log(module1);
import * as module2 from 'module2';
console.log(module1);
is effectively (not exactly) the same as
const module1 = require('module1');
const module2 = require('module2');
console.log(module1);
console.log(module2);
Because of this quirk, in your current code, admin.firestore() is incorrectly pointing at your live Firestore database and test.firestore is pointing at your test Firestore database. This is why the document doesn't exist, because it exists on your test database, but not your live one.
This is why the documentation you linked uses require statements, and not the import syntax.
// this is fine, as long as you don't call admin.initializeApp() before overriding the config and service account as part of test's initializer below
import * as admin from 'firebase-admin';
import 'jest';
// Override the configuration for tests
const test = require("firebase-functions-test")({
databaseURL: "https://mydb.firebaseio.com",
projectId: "myproject",
}, './service-account.json');
test.mockConfig({});
// AFTER mocking the configuration, load the original code
const { makeUpperCase } = require('../src/index');
describe('basicTest', () => {
let wrapped: any;
beforeAll(() => {
wrapped = test.wrap(makeUpperCase);
});
test('converts input to upper case', async () => {
const path = 'test/testId';
const data = { input: 'a simple test' };
const snap = await test.firestore.makeDocumentSnapshot(data, path);
await wrapped(snap);
const after = await admin.firestore().doc(path).get();
expect(after.data()!.input).toBe('A SIMPLE TEST');
});
});