Hello guys Could you please recommend sources where to read

Question

Hello guys Could you please recommend sources where to read listen about Kotlin code structure As I can see Kotlin doesn t have package as a first class citizen no package private access to members It suggests to use modules instead but they are slightly different thing and I haven t seen any best practices of using Kotlin modules

Czar · Answer

romster · Answer

Thank you but there is nothing about modules and internal visibility best practices there

Czar · Answer

Sorry I don t understand what you mean then

Czar · Answer

internal is the same as package but with additional restriction to the same jar

romster · Answer

So it is useful only for libraries developers isn t it

Czar · Answer

why within project it acts as package private

Fleshgrinder · Answer

But requires special build setup with separation into different directories and what not Package private is a little easier to apply ad hoc

romster · Answer

Except the code organisation that package stuff in java made some methods more testable without necessity to make them public Maybe it wasn t idiomatic but it was a very common approach Kotlin closes this backdoor but doesn t offer any way to test not public methods as I can see

Czar · Answer

generally I believe private methods should not be tested if they have to be tested something is wrong in the design or you re overtesting things

Fleshgrinder · Answer

You can easily access your internal stuff in your tests if you set it up with a dedicated module and I agree private stuff should not be tested

romster · Answer

Well thank you guys But I can t agree with this position because I prefer to limit public API and to decompose one big method into small private not only class private pieces which could be easily tested but it s not allowed This approach with do not test private method or make them public seems restriction driven to me Anyway do you know any open source project with Kotlin modules which you can call reference implementation of good structure

Czar · Answer

There are no official ones but you could take a look at cbeust s < C0BRKJ9K9|kobalt> build system or < C5UPMM0A0|arrow> library or any other popular opensource app lib written in kotlin plenty of them on GitHub

Czar · Answer

And it s not really gt do not test private method or make them public It s more like Test all public methods so that private ones don t need to be tested If by testing the public method you cannot ensure correctness and absolutely need to test private methods then most probably there s something dangerously wrong in the design I understand that `internal` stuff is not truly private and should be tested that just means keep your tests in the same module as your code

Czar · Answer

e g in my project I use gradle if I have internal class or a class with internal methods and I m testing it this setup works perfectly fine ``` src main kotlin com example InternalClass kt src test kotlin com example InternalClassTest kt```

Fleshgrinder · Answer

< romster> the last example from < Czar> show exactly what I was talking about With private I really meant private and tiny helpers that are only there to make the code more readable hence easy to test automatically via the public stuff that uses them However `internal` is different and you can easily test them As I said it s more cumbersome to set up compared to a proper package visibility and I would love to see it in Kotlin but right now that s what we have ``` lib src main kotlin com example PublicClass kt lib src main kotlin com example InternalClass kt lib src test kotlin com example PublicClassTest kt lib src test kotlin com example InternalClassTest kt app src main kotlin com example NoAccessToInternalClass kt ```