#cases [{output #err <invalid value>
         select missing-side}
        {output #err <invalid value>
         select repeat-only}
        {output #err <invalid value>
         select conflicting-sides}
        {output #err <invalid value>
         select both-left}
        {output #err <invalid value>
         select both-right}
        {output #err <invalid value>
         select unknown-option}
        {output #err <invalid value>
         select text-options}
        {output #err <mismatch type>
         select opts-string}
        {output #err <mismatch type>
         select opts-list}
        {output #err <mismatch type>
         select opts-null}
        {output #err <mismatch type>
         select text-opts-null}
        {output #err <mismatch type>
         select source-null}
        {output #err <mismatch type>
         select source-number}
        {output #err <mismatch type>
         select text-source-null}
        {output #err <mismatch type>
         select text-source-number}
        {output #err <mismatch type>
         select text-null}
        {output #err <mismatch type>
         select text-number}
        {output #err <arity mismatch>
         select missing}
        {output #err <arity mismatch>
         select old-arity}
        {output #err <arity mismatch>
         select extra}]