anchor.diff:        {{a,b,2},[{['$1','$2'],[{'==','$1',1},{'=/=','$2',a}],[]}],[local]}}
        ,{"a:b(X,y)when not is_atom(X) -> return",
          {{a,b,2},
  -        [{['$1',y],[{'not',{is_atom,'$1'}}],[{return_trace}]}],
  +        [{['$1',y],[{'not',{is_atom,'$1'}}],[{exception_trace}]}],
           [local]}}
        ,{"a:b(X,y)when element(1,X)==foo, (X==z)",
          {{a,b,2},
  
positive.code:        {{a,b,2},[{['$1','$1'],[],[]}],[local]}}
       ,{"a:b(X,y)",
         {{a,b,2},[{['$1',y],[],[]}],[local]}}
       ,{"a:b(X,1)",
         {{a,b,2},[{['$1',1],[],[]}],[local]}}
       ,{"a:b(X,\"foo\")",
         {{a,b,2},[{['$1',"foo"],[],[]}],[local]}}
       ,{"a:b(X,y)when is_atom(Y)",
         unbound_variable}
       ,{"x:c([string])",
  
negative.code:         [local]}}
       ,{"a:b(X,X) -> return;stack",
         {{a,b,2},
          [{['$1','$1'],[],[{exception_trace},{message,{process_dump}}]}],
          [local]}}
      ]).
  
  