How to mock firebase.firestore namespace?

[Acterion]

Problem:
I am using firebase.firestore.Timestamp.now() in my entities constructors in the main app.
I need to be able to use them inside tests as well.
Just importing ts file with entities gives me an error: TypeError: Cannot read property 'Timestamp' of undefined.

I searched everywhere but can't find a solution to this problem. Can someone help? (Ideally with a code example)

[dmurvihill]

Can you post your non-working code? We will be unable to get anywhere without seeing what you are seeing.