"parse_tcx_file handles valid but empty TCX"
'<?xml version="1.0" encoding="UTF-8"?>
<TrainingCenterDatabase xmlns="http://www.garmin.com/xmlschemas/TrainingCenterDatabase/v2">
  <Activities>
  </Activities>
</TrainingCenterDatabase>'
"parse_gpx_file handles valid but empty GPX"
'<?xml version="1.0" encoding="UTF-8"?>
<gpx version="1.1" xmlns="http://www.topografix.com/GPX/1/1">
</gpx>'
"parse_activity_file handles different file extensions"