> But you should know this from your functional requirements, right? Functional requirements describe observable behaviour. You can't write any meaningful test

> But you should know this from your functional requirements, right? Functional requirements describe observable behaviour. You can't write any meaningful tests for that behaviour until a lot of your code is written. Yet somehow in all the discussions there's this unexplaned leap from "you have the requirements" -> "well you just write a unit test for your function first, and then code it". My functional requirements come in the form of "Given publisher A in Country B and contract requirements C the service must return D for a subset of products E", for multiple combinations of A, B, C, D, and E. And where each of those may and will require lookups in external services and databases.