PR updates swift version used on Travis CI linux job which enables automatic test discovery on Linux platform. Unit tests and SPM target corrected with found errors.
Had to update Linux distributive from Trusty to Xenial since Ubuntu 14.04 does not come with Swift 5.4 support, and minimal supported version is Ubuntu 16.04 (as found here) which is represented with Xenial dist on Travis.
PR updates swift version used on Travis CI linux job which enables automatic test discovery on Linux platform. Unit tests and SPM target corrected with found errors. Had to update Linux distributive from
TrustytoXenialsince Ubuntu 14.04 does not come with Swift 5.4 support, and minimal supported version is Ubuntu 16.04 (as found here) which is represented withXenialdist on Travis.