Overall, I think the feature is important to have, but I don’t understand some 
of the aspects of the proposal. I also don’t think there is a real focus for 
clarity on the types of testing that are being supported here. The implication 
is that unit tests are what this is being targeted, but is this proposal 
specifically limiting to those particular types of tests? If so, why? If not, 
some of the aspects really don’t make much sense to be defaulted into.

> Additionally we will support directories called FooTests. This layout style 
> is prevalent in existing open source projects and supporting it will minimize 
> vexation for their authors. However in the interest of consistency and the 
> corresponding reduction of cognitive-load when examining new Swift packages 
> we will not  recommend this layout. For example:
> 
>     Package
>     └── Sources
>     │   └── Foo.swift
>     └── FooTests
>         └── Test.swift

Why support something that that is not going to be recommended? Prevalence of 
something seems like a poor choice, especially when you are going to 
specifically not recommend to use it. Also, the proposal already mentioned an 
override mechanism to allow these to be specified. This seems like something 
that could easily be cut.

> Additionally, we propose that building a module also builds that module's 
> corresponding tests. Although this would result in slightly increased build 
> times, we believe that tests are important enough to justify this (one might 
> even consider slow building tests to be a code smell). We would prefer to go 
> even further by executing the tests each time a module is built as well, but 
> we understand that this would impede debug cycles.

Re-building tests all of the time is a huge time waste. Executing those tests 
even more so (also see original question on the types of tests being 
supported). Not only that, in production software, it’s very often the case 
that there are levels of tests that get run because of the shear amount of them 
that exist and the time involved to run them. In addition to levels, there are 
classifications of tests (perf, robustness, memory, stress, fuzzing, etc…).

This is something that should be an opt-in. The most basic example of this is 
refactoring a code base (which is later briefly mentioned at the end o the 
proposal). The first step is getting the code compiling for the project. It’s 
not true that the very next step you take is fix up the tests, especially in 
the cases that the refactoring/changes are exploratory.

> In the future, we may choose to promote the --test option to be a subcommand 
> of the swift command itself:
> 
> $ swift test
> 
> However, any such decision would warrant extensive design consideration, so 
> as to avoid polluting or crowding the command-line interface. Should there be 
> sufficient demand and justification for it, though, it would be 
> straightforward to add this functionality.


This doesn’t make sense to me. It’s either straightforward, or it requires 
extensive design consideration. I personally strongly dislike coupling the 
notion of building with test execution, so I would much rather see “swift test” 
used, especially with a look into the future where it’s going to be asked for 
the ability to run categories of tests and filter to a particular set of tests 
to be run.

Another real problem with this type of design, is that is makes more advanced 
build systems very complicated to make. For example, distributed builds that 
bring together all of the compiled bits to run tests on get blocked because the 
build command starts to expect certain intermediate output. This is a real 
problem my previous team still has to this day with xcodebuild and actively 
prevents us from doing this exact thing with standard tools from Apple, so we 
have to basically roll our own. I see this design following in the exact same 
footsteps.

I think a lot of the design would be clarified by changing all of “by 
convention” items into realized default values in the Package.swift file. That 
would clearly demonstrate how the work and how we can change them.

-David


> On Jan 5, 2016, at 11:06 AM, Rick Ballard via swift-evolution 
> <[email protected]> wrote:
> 
> Hello Swift community,
> 
> The review of “Swift Testing” for the Package Manager begins now and runs 
> through Thursday, January 7th. The proposal is available here:
> 
>       
> https://github.com/apple/swift-evolution/blob/master/proposals/0019-package-manager-testing.md
> 
> For this particular review, please note that a significant amount of 
> discussion history is available in the original pull request for the proposal:
> 
>       https://github.com/apple/swift-evolution/pull/51
> 
> Reviews are an important part of the Swift evolution process. All reviews 
> should be sent to the swift-evolution mailing list at
> 
>       https://lists.swift.org/mailman/listinfo/swift-evolution
> 
> or, if you would like to keep your feedback private, directly to the review 
> manager.
> 
> What goes into a review?
> 
> The goal of the review process is to improve the proposal under review 
> through constructive criticism and, eventually, determine the direction of 
> Swift. When writing your review, here are some questions you might want to 
> answer in your review:
> 
>       * What is your evaluation of the proposal?
>       * Is the problem being addressed significant enough to warrant a change 
> to Swift?
>       * Does this proposal fit well with the feel and direction of Swift?
>       * If you have you used other languages or libraries with a similar 
> feature, how do you feel that this proposal compares to those?
>       * How much effort did you put into your review? A glance, a quick 
> reading, or an in-depth study?
> 
> More information about the Swift evolution process is available at
> 
>       https://github.com/apple/swift-evolution/blob/master/process.md
> 
> Thank you,
> 
>       - Rick
>         Review Manager
> _______________________________________________
> swift-evolution mailing list
> [email protected]
> https://lists.swift.org/mailman/listinfo/swift-evolution

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