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Amen. I have been frustrated at many jobs where developers were so proud of endlessly writing mocks and spending more time on their tests than on core function

Amen. I have been frustrated at many jobs where developers were so proud of endlessly writing mocks and spending more time on their tests than on core functionality. Over time I have favored very basic unit tests and leaning in more on automated integration and regression tests. I know the theory of unit tests catching things earlier, I just don’t think it matters in practice.

sanderjd 4y ago
I think in practice unit tests are both the most and least useful tests. Unit tests of code that just generates output as a function of input are the most useful, and unit tests of code that just glues together a bunch of side effects are the least useful. I like to find ways to structure things so that it is mostly comprised of the first kind of code, and has so little logic in the second kind of code that it's easy to justify not unit testing it.
alpaca128 4y ago
I once saw type checking presented as kind of an alternative to unit tests which doesn't rely on the assumption that developers write good tests, and I really like that viewpoint. A powerful type system can prevent many bugs, doesn't need additional test code and doesn't make any assumptions. Of course it's not necessarily a full replacement, but it's definitely better and more time efficient than bad tests.
- sanderjd 4y ago
  Yes, static analysis of types can eliminate a big class of unit tests (basically just checking pre- and post- conditions on types), which is a big part of why it's great. But most unit tests should be for logic. But that's why they aren't very useful for "glue" methods which just thread things through different dependencies - they shouldn't have much interesting logic.
- codethief 4y ago
  > Of course it's not necessarily a full replacement I'd actually say: Not in the slightest. A type system just rules out illegal input values[0] but it won't ensure that your business logic is correct. And even that[0] is not entirely correct because, most of the time, a type system just rules out some illegal values but not all of them, because it cannot represent all possible constraints. Gary Bernhardt discussed this whole type checking vs. tests debate at length here: https://www.destroyallsoftware.com/talks/ideology https://www.destroyallsoftware.com/talks/ideology

sanderjd 4y ago

I think in practice unit tests are both the most and least useful tests. Unit tests of code that just generates output as a function of input are the most useful, and unit tests of code that just glues together a bunch of side effects are the least useful. I like to find ways to structure things so that it is mostly comprised of the first kind of code, and has so little logic in the second kind of code that it's easy to justify not unit testing it.

alpaca128 4y ago

I once saw type checking presented as kind of an alternative to unit tests which doesn't rely on the assumption that developers write good tests, and I really like that viewpoint. A powerful type system can prevent many bugs, doesn't need additional test code and doesn't make any assumptions. Of course it's not necessarily a full replacement, but it's definitely better and more time efficient than bad tests.

sanderjd 4y ago
Yes, static analysis of types can eliminate a big class of unit tests (basically just checking pre- and post- conditions on types), which is a big part of why it's great. But most unit tests should be for logic. But that's why they aren't very useful for "glue" methods which just thread things through different dependencies - they shouldn't have much interesting logic.
codethief 4y ago
> Of course it's not necessarily a full replacement I'd actually say: Not in the slightest. A type system just rules out illegal input values[0] but it won't ensure that your business logic is correct. And even that[0] is not entirely correct because, most of the time, a type system just rules out some illegal values but not all of them, because it cannot represent all possible constraints. Gary Bernhardt discussed this whole type checking vs. tests debate at length here: https://www.destroyallsoftware.com/talks/ideology https://www.destroyallsoftware.com/talks/ideology