You're asking yourself: how to practically isolate my domain code from moving parts like databases or external systems, APIs... in the simplest way either. How can I do that without integration testing. Are Unit Test sufficient? Can I apply TDD literally?
I've heard about mock as a perfect solution to test my dependencies.
Well, we need to talk. Better than that: we need to code!
Let's work on a very concrete and representative example. And let's mob it!

Format: 3/4h ( live coding/workshop) ; fish bowl MOB programing
Isolate domain rules and invariants
Add external system and test then
Learn about test doubles : stubs, spy, fake, mocks
When and how to use it? How to avoid mocks.

We will work on Concrete examples:
- ask time / generate random values (like UUIDs)
- send a mail / print an invoice
- access to an external resource (like a file)
- invoke a read/write repository
- summon an API
Showing what’s legitimate and what’s beyond reason