[SR-1589] Add non-throwing testCase() wrapper function.

[ddunbar]

• This is useful in clients which would like to use Swift type inference to
  define the allTests array. If none of the tests in the class throw, Swift
  will infer the type of that array as (String, (T) -> () -> ()) which is not
  convertible to the type expected by the testCase method.
• Resolves: https://bugs.swift.org/browse/SR-1589

[briancroom]

I don't think it's necessary to add this overload, because the type conversion should allow the existing test(_:) function to be used (no tuples involved in the argument type).

[ddunbar]

Ah yes, good point. Fixed and rebased (c65b335).

[briancroom]

Thanks for the PR @ddunbar! This is a nice improvement. I left one minor comment on the code.

A little testing seems to indicate that the alternative allTests form can be used in all cases, including when mixing throwing and non-throwing tests. So I wonder if we should actually update our tests and change the recommended form to use this now?

class FooTests: XCTestCase {
  func testFoo() {}
  // Notice use of type inference to avoid boilerplate.
  static var allTests = {
    ("testFoo", testFoo)
  }()
}

[briancroom]

@swift-ci please test

[ddunbar]

Yes, the alternative form will work in all cases now, because either of the types Swift infers will work. I think it would be a good idea to update to this as the standard recommendation as it reduces some of the redundant boilerplate that currently needs to be copied and then modified (to change the test case name).

I can follow up on that.

[ddunbar]

@swift-ci please test

[briancroom]

The Linux test failure is caused by the ongoing issues with Foundation's test suite. I tested it locally and it looks good to go.

@ddunbar If you don't have time, I have no problem updating the other tests and docs here myself. Thanks for bringing this up!