Unit testing bigger units
The previous section introduced the idea of surrounding our domain model with test doubles for every port. This gives us some interesting opportunities to discuss in this section. We can test units that are as large as a user story.
We’re familiar with unit tests as being things that test in the small. There’s a good chance you’ll have heard somebody say that a unit test should only ever apply to a single function, or that every class should have one unit test for every method. We’ve already seen how that’s not the best way to use unit tests. Tests like those miss out on some advantages. We are better served by thinking of tests as covering behavior instead.
The combined approach of designing with the hexagonal architecture and testing behaviors instead of implementation details leads to an interesting system layering. Instead of having traditional layers, as we might do in a three-tier architecture, we have circles...
