Firebase | Firestore | Firestore junit test | deep stubbing mockito

This is a sample code how to perform deep stubbing mockito on firestore

you need to mock all the 

public class FirestoreClientTest{

@Mock

Firestore firestore;

@Mock

DocumentReference documentReference;

@Mock

CollectionReference collectionReference;

@Mock

ApiFuture apiFuture;

@Mock

QuerySnapshot querySnapshot;

@Test

public void test(){

when(firestore.collection(any(String.class)).thenReturn(collectionReference);

when(collectionReference.document(any(String.class)).thenReturn(documentReference);

when(documentReference.get()).thenReturn(apiFuture);

when(apiFuture.get()).thenReturn(querySnapshot);

UserInfo userInfo = firestore.getUserDetails();

//Assert statements

}

}