Add swift-testing dependency

[Kyle-Ye]

Sometimes the XCTAssert's output for diff is not very clear.

(For example I have to copy paste a few times from the result of Swift.print or the failure result of XCTAssertEqual to make it happy)

XCTAssertEqual failed: ("Document @1:1-4:2
└─ BlockDirective @1:1-4:2 name: "Image"
   ├─ Argument text segments:
   |    @2:1-2:25: "  source: "example.png","
   |    @3:1-3:23: "  alt: "Example image""") is not equal to ("Document @1:1-4:2
└─ BlockDirective @1:1-4:2 name: "Image"
   ├─ Argument text segments:
   |    @2:1-2:25: "  source: \"example.png\","
   |    @3:1-3:23: "  alt: \"Example image\""")

I can certainly solve it in the end. But if we can migrate to use swift-testing as our test framework, it will be more clear and more efficient.

[Kyle-Ye]

Here is something blocking items preventing the adoption in Swift-DocC project IMO:

• Missing Windows Support due to the macro issue on Windows Platform
• Minimal Swift version is currently 5.9
• Currently it is in active development stage. Not source stable.
• Currently it has a dependency on swift-docc-plugin.(Maybe wrap it on) So there may be cycle dependency issue if we want to use it in swift-docc-plugin or swift-docc-symbolkit. cc @grynspan
• Currently it has a dependency on Swift-Syntax of Swift 5.9. Hope SwiftPM will have a syntax declaration later to mark a dependency as testTarget only so our downstream user won't get swift-testing and Swift-Syntax dependency.

[grynspan]

Hi Kyle! swift-testing has a permanent dependency on Swift 5.9 due to its use of macros. It does not have a declared dependency on swift-docc-plugin.

[Kyle-Ye]

Hi Kyle! swift-testing has a permanent dependency on Swift 5.9 due to its use of macros. It does not have a declared dependency on swift-docc-plugin.

I'll update the statements. I checked it again and found my mistake here.

[grynspan]

Currently it has a dependency on Swift-Syntax of Swift 5.9. Hope SwiftPM will have a syntax declaration later to mark a dependency as testTarget only so our downstream user won't get swift-testing and Swift-Syntax dependency.

Please file an issue against SwiftPM for this?

[Kyle-Ye]

Please file an issue against SwiftPM for this?

Got it. Filed via swiftlang/swift-package-manager#7007

[d-ronnqvist]

Here is something blocking items preventing the adoption in Swift-DocC project IMO:

I agree with those items.

[Kyle-Ye]

Have tried swift-testing for a while. I think it's ready for production use. (Won't make it default or rewrite all test case into it before Swift 6.)

Add a PR to draft the integration. See #175

Here is something blocking items preventing the adoption in Swift-DocC project IMO:

• Missing Windows Support due to the macro issue on Windows Platform
• Minimal Swift version is currently 5.9
• Currently it is in active development stage. Not source stable.
• Currently it has a dependency on swift-docc-plugin.(Maybe wrap it on) So there may be cycle dependency issue if we want to use it in swift-docc-plugin or swift-docc-symbolkit. cc @grynspan
• Currently it has a dependency on Swift-Syntax of Swift 5.9. Hope SwiftPM will have a syntax declaration later to mark a dependency as testTarget only so our downstream user won't get swift-testing and Swift-Syntax dependency.

• Macro issue on Windows platform is already fixed IIRC.
• We do not need to really bump the version. All the code is guarded by a feature flag.
  • We just added a new Package@swift-5.10.swift/Package@swift-6.0.swift. So downstream user who have lower Swift version can still use the latest swift-markdown.
  • We only add swift-testing dependency in development/CI. So that downstream user won't get swift-testing and swift-syntax dependency transparently.
    • The upstream SwiftPM do not think this is a problem and have no intend to support it. So I just supported manually here using some env trick. See Add devDependencies support in SwiftPM swift-package-manager#7007
• I have used it since 0.1. The API is pretty stable for me. Most API we use is just #expect and #require.

[Kyle-Ye]

• We do not need to really bump the version.

That said I still hope #135 can be merged since we have discussed and approved it on SDWG meeting. :)

[grynspan]

Have tried swift-testing for a while. I think it's ready for production use. (Won't make it default or rewrite all test case into it before Swift 6.)

This package remains experimental. We do not consider it ready for production use at this time.

[Kyle-Ye]

Have tried swift-testing for a while. I think it's ready for production use. (Won't make it default or rewrite all test case into it before Swift 6.)

This package remains experimental. We do not consider it ready for production use at this time.

Of course. It won't be production ready before 1.0 release.

Sorry for the incorrect wording. I mean we can consider making it for experiential usage under a feature flag.

[d-ronnqvist]

I don't think we should have experimental dependencies. It's better to wait until swift-testing is considered ready for production.

[tayloraswift]

i encourage swift-markdown (and other packages) to adopt swift-testing. my experience at our organization is that not doing so disincentivizes developers from writing tests, as all tests written against a legacy framework would need to be rewritten later. since we are constantly expecting swift-testing 1.0 to be “just around the corner”, the quality of code can deteriorate markedly as test writing gets repeatedly deferred.

[Kyle-Ye]

As swift-testing is bundled with Xcode 16 beta now and will probably be release together with Xcode 16, can we revisit this policy? @d-ronnqvist

Also would you mind helping to explain the current situation of swift-testing in swift-toolchain? It is not clear to me whether swift-testing will be available in the next Swift 6 toolchain for non-Darwin platform(Linux & Windows)? @grynspan

[d-ronnqvist]

As swift-testing is bundled with Xcode 16 beta now and will probably be release together with Xcode 16, can we revisit this policy? @d-ronnqvist

Also would you mind helping to explain the current situation of swift-testing in swift-toolchain? It is not clear to me whether swift-testing will be available in the next Swift 6 toolchain for non-Darwin platform(Linux & Windows)? @grynspan

I may be wrong about this but my understanding is that this would require a Swift 6 toolchain (Xcode 16) for building on all platforms. If that is correct, we shouldn't adopt Swift Testing yet. We still want to be able to build Swift Markdown, Swift SymbolKit, Swift DocC, etc. with a Swift 5.9 toolchain on all platforms.