Use '_test' package when appropriate

[ammario]

If the -exported flag is set, it makes more sense to use the _test package by default in the generated code.

[cweill]

Can you please give me an example? I'm not exactly sure what you mean by "_test package".

[ammario]

When testing only exported functions, tests are encouraged to use the <package>_test package instead of just <package>. It has the effect of making the user be more careful about what he exports and forces him to only test exported methods. It is the exception to the only one package per directory rule.

[cweill]

Oh wow, TIL! I had never heard of that before, but I just tested it out, and it works. Since which Go version is that a thing?

Could you please point me to some documentation for this feature? I have trouble finding it. I would need to read about the best practices before implementing such a feature.

[ammario]

Unfortunately I can't find any official documentation of the feature... There's a good amount of blog posts and stackoverflow answers alluding to it positively though. There doesn't seem to be a general consensus on when to use it. The official blog uses it here but doesn't specify why. I assume it's to isolate the scope of test related variables.

Maybe it would be best to just make it optional?

[itsjamie]

The other time I've seen it used is to make ExampleXXX functions copy and paste friendly. Since they need to be compilable, if you write them in the regular package name you won't have the package name for your example code. https://blog.golang.org/examples

Although I like the idea of -exported using it to help enforce the public API compatibility.

[SteelPhase]

This feature is documented here.

Test files that declare a package with the suffix "_test" will be compiled as a separate package, and then linked and run with the main test binary.

This would be a great feature to have

I would like to see this feature too. Testing a library from a _test package proves that the library can be used by others.

[IlyasYOY]

Hello! I tried to come up with solution, now it's not great.

If you @cweill think I'm going in the right direction and you are ready to review the contribution, I'd be glad to finish the solution.