[XCTestObservation] Add test bundle observation

[modocache]

Apple XCTest defines more methods on its XCTestObservation than swift-corelibs-xctest does. Here we add two of these missing methods:

• testBundleWillStart()
• testBundleDidFinish()

The documentation for the two methods is taken from Apple XCTest's headers.

[mike-ferris]

@swift-ci please test

[mike-ferris]

I guess this maps reasonably. What does mainBundle return for a linux command line tool (or an OS X one, for that matter)?

[modocache]

Hmm, the Linux CI failure is an unrelated failure in the Swift test suite--strange, since we --skip-test-swift for the build preset. Maybe that flag doesn't skip validation tests... I'll modify our preset such that we don't get blocked by intermittent failures in Swift proper.

As for command-line tool bundles:

• On OS X, using Xcode 7.2's command-line tool project template, printing [NSBundle mainBundle] outputs: NSBundle </Users/bgesiak/Library/Developer/Xcode/DerivedData/BundleBundleOnTheWall-ewdkqrksmgkyedgcxaivcypxfoaq/Build/Products/Debug> (loaded)
• On Linux, in a simple Swift executable linked with Foundation, NSBundle.mainBundle() returns a temporary bundle at a path like /tmp/tmpZtm9Of.

I'm not sure how similar these two are, but I also think improving the bundle behavior could be something we improve upon later. I consider the fact that the announcements are made with the same signature as Apple XCTest to be the main improvement here.

[mike-ferris]

Agreed.

[modocache]

@mike-ferris-apple Great! Normally I'd ask you to kick off CI again, but I'm not entirely sure it's been fixed. I've tested this on Linux and OS X and it definitely works for me, so... merging! 😁