Firestore Unit Testing

[akapur99]

What We Want To Do

Implement (in-memory) unit tests for calls to Firebase firestore which actually test functionality (similar to SQLite)

What are We Currently Doing

We are currently jest mocking the firestore methods with empty mock functions, without really testing functionality. We need to expand on this to:

• 1 - Add get() method to the mocks
• 2 - Add unit tests to at least see that the methods are getting called with the correct parameters/data

Methods Tried in the Past

Firebase Emulation

This would be ideal BUT not ideal for in-memory local unit tests as it requires a separate process (not in-memory). We should might want to be setting this up in the future though, alongside BDD/integration testing

Firebase Functions Test

• firebase-functions-test is also not ideal as it is built specifically for Cloud functions which we are not using (but can switch to)
• Furthermore, Firebase reccomends using these for online tests, and dissuades from siloed offline testing:

Using offline mode is generally not recommended if you have Cloud Firestore or Realtime Database functions, since it greatly increases the complexity of your test code.

firebase-mock

• Ensure you are using the fork by dmurvihill not the main repo (original repo owner is not maintaining it)
• Seems ideal for our purposes however when listening for doc changes triggers - it doesn't have the latest querySnapshot.docChanges() method. It might still be possible to use this package but would require moving to a firebase-functions implementation of triggers/listeners for Firebase doc changes
• Have also made an issue for the above in the repo - worth revisiting if it gets fixed.
• Checkout branch firebaseMocking(https://github.com/mojaloop/pisp-demo-server/tree/firebaseMocking) for attempted implementation

firebase-mock + Basic Jest Mocking

• Briefly tried (which can be seen in the firebaseMocking`(https://github.com/mojaloop/pisp-demo-server/tree/firebaseMocking) implementation), to keep both sets of mocks and only use the npm package when doing unit tests on the firebase methods directly. It works but is too janky/messy/confusing to have.

ts-mock-firebase

• Both @eoln and I were unable to install or use this package.

firebase-nightlight

• Too old and doesn't support enough features