When an ABNF grammar is opened in the grammar editor, the coverage testset is automatically created if it does
not already exist (this behaviour can be customized in the preferences). A coverage testset resource has the same name as the grammar resource, except for the
extension, which is .grd.
All the tools that can add ING or OOG sentences to a coverage testset for a given grammar automatically create the coverage testset file if it does not exist.