There must be module with test assertions in Phobos

[Atila Neves]

On Thursday, 30 March 2023 at 17:01:26 UTC, Dmytro Katyukha wrote:
> But, this feature is not convenient/usable without standard set 
> of `assert*` methods, that could display human-readable output 
> in case of error (what value expected, and what value we got).
> Because of absense of such expected functionality, there are 
> some set of third-party libraries that implement good and 
> readable assertions. But, most popular assertion libraries 
> depend on 
> [unit-threaded](https://code.dlang.org/packages/unit-threaded) 
> that is large test runner.

You can depend on only the assertions dub subpackage, which is 
tiny, and then use the standard runner from druntime.

> And it is strange, when you try to add small and simple library 
> to dependencies of your project, but it brings whole 
> unit-threaded package to your project.

That's a dub bug. If a project lists a dependency only in the 
unittest configuration, it adds it to the transitive list of 
dependencies, which is obviously nonsense.

> And i think, in significant amount of cases, this dependency is 
> added just because standard set of asserts absent in standard 
> library.

And running in threads, and running specific tests, and...

> I think, for small libraries there is no sense to depend on 
> large test runner. Ususally it is enough to use standard test 
> runner.

To each their own, I'd use a "proper" library every time because 
of the developer experience.

> Just take a look at python's assertions from standard library 
> [unittest](https://docs.python.org/3/library/unittest.html#assert-methods)

None of those are needed if using pytest, which I'd recommend 
anyone writing Python code to do. One uses the standard Python 
`assert` and it prints error messages that make sense. It's 
magic, and it's magic I'd want for D.

> I think, implementation of this list of asserts in the Phobos 
> will allow users to start use unittest much easier.

Nearly every test assertion is of equality. It's nice to have the 
others when needed, but they're not a good 99.9% of the time.

> Also, the question to authors of assert libraries (like 
> [unit-threaded:assertions](https://code.dlang.org/packages/unit-threaded%3Aassertions), [dshould](https://code.dlang.org/packages/dshould), etc): what do you think about contributing assertions to Phobos?

It's definitely an idea.