Test discovery for Swift Testing

[Uncommon]

Create a mechanism for tests to be discovered and run in Swift Testing.

[Uncommon]

How @Test works on a function:

• @Test creates a peer enum whose name contains the magic string __🟠$test_container__
• The enum contains static var __tests: [Testing.Test] which contains the Test instance for this test function
  • instance is created with __function(), which is supposed to be only for use by the macro but the Test constructors are not public so there is no other option
• The function enumerateTypes(withNamesContaining:) is used to find all types containing the magic string
• The property Test.all uses that function to discover the specially named types and aggregate their __tests
• Test.all is used by Runner.Plan.init(configuration:) and entryPoint() when no list of tests is given
• That seems to leave Runner.Plan.init(tests:configuration:) as a way to specify a custom list of tests
  • called by Runner(testing:configuration:) which is currently only used by unit tests

[Uncommon]

Deferred because the public API doesn't expose the needed functionality. They say they're working on this.

[Uncommon]

Swift Testing's test discovery works via C++ code that examines low-level Swift runtime metadata. They want to come up with something better, and I'd rather wait and see what they come up with.

[Uncommon]

Maybe this will be replaced by implementing #8