This adds a unit test target to the Xcode project and the Swift package. It can be used for unit tests of the Swift layer and contains some basic tests of the Swift interface already.
rdar://52447946
I added some rudimentary tests for the Swift interface and want to use that target to write tests for the Swift interface of the build database (instead of having an example target).
Question: Should we add swift test to the utils/build-and-test script?
该提问来源于开源项目：apple/swift-llbuild
