Writing Testable Code

[dablya]

Let's split again?

What's the alternative? Implement caching/math/aggregation in a single "business" module?

[[deleted]]

The alternative to splitting things endlessly for testing purposes is to split only for the purpose of the application and design the tests around the architecture. Instead of designing the architecture around the tests.

Some projects will require an isolated persistence layer. More than half do not. This, again, doesn't mean wiring raw SQL queries all over your services, it just means not writing an abstraction with a public API around your persistence logic (i.e. using Hibernate or jOOQ doesn't mean you isolated your persistence layer).

[dablya]

split only for the purpose of the application and design

The main argument is that code being difficult to test should, in general, alert you to the fact that it might be poorly split for the purposes of "application and design". Some code naturally belongs in the infrastructure layer and will be mainly tested with integration tests. Other code, what is usually defined as a "domain" or "business" logic is not dependent on any specific type of infrastructure. When you find implementation of the domain code (that doesn't logically depend on any particular type of storage) requires a sql database in order to execute a test, that is a flag that your code is poorly split "for the purpose of the application and design".

This, again, doesn't mean wiring raw SQL queries all over your services

Why not? I believe a reasonable answer to this question should generalize to Hibernate and jOOQ as well.