This tests platform specific system font styles. If any of the styles appear in monospace the test fails.
caption: normal normal normal normal 13px/normal system-ui
icon: normal normal normal normal 13px/normal system-ui
menu: normal normal normal normal 13px/normal -apple-menu
message-box: normal normal normal normal 13px/normal system-ui
small-caption: normal normal normal normal 11px/normal system-ui
status-bar: normal normal normal normal 10px/normal -apple-status-bar
-webkit-mini-control: normal normal normal normal 9px/normal system-ui
-webkit-small-control: normal normal normal normal 11px/normal system-ui
-webkit-control: normal normal normal normal 13px/normal system-ui