Does your script running xcodebuild break every time you update Xcode because the Simulator version you were pointing at is not there anymore? No worries, there is a simple keyword you can use in the destination option to always run the most recent Simulator version.
xcrun xcodebuild \
-workspace Bench.xcworkspace \
-scheme BenchUITests \
-destination 'platform=iOS Simulator,name=iPhone 6,OS=latest' \
-sdk iphonesimulator \
testOS=latest does the trick 👍.
Happy coding, and leave the codebase better than you found it.