javascript - How do you mock Firebase Firestore methods using Jest?

Question

I have a series of functions, each performing various firestore interactions. How do I use Jest to mock these firestore calls? I would like to avoid using a library.

When I use jest.mock("firebase/app") and jest.mock("firebase/firestore") and other variations, I either get null TypeErrors, or errors indicating I am still referencing the actual import and not the mock: Error: ... make sure you call initializeApp().

For example, a simple function I want to test:

import firebase from "firebase/app";
import "firebase/firestore";

export const setDocData = (id, data) => {
  const newDoc = {
    created: firebase.firestore.FieldValue.serverTimestamp(),
    ...data
  };
  firebase
    .firestore()
    .doc("docs/" + id)
    .set(newDoc);
};

Notice how firebase is imported as usual, then firestore is imported a side effect. Also notice how firestore is called first as a function, then later referenced as a property. I believe this is the source of my trouble.

Answer 1

Waitting for answers