Hi Everyone,
Even with the latest Xcode(10.1) and Watch OS 5 , we cannot automate watch apps. Possibly because, Apple does not provide support to build an app exclusively for Apple watch(there is no target to be set for apple watch in Xcode). It comes as a single bundle for iPhone with watchkit. However using PivotalCoreKit framework there was a possiblity to test watch apps until WatchOS 2.
Please update if anyone is able to automate watch apps.