anchor.diff:    , ?_assertEqual({true , [V0]    , [AV]}, match(A, [V, V0]))
     ].
   
  -command_match_test_() ->
  +match_command_test_() ->
     C  = cmd("c"),
     A  = arg(undefined, "c"),
     CT = cmd("c", true),
  
positive.code:     %% Either...
    ].
  
  optional_match_test_() ->
    OA = opt("-a"),
    OB = opt("-b"),
    OX = opt("-x"),
  
negative.code:   , ?_assertEqual({true , [A]   , [AT]}, match(A, [AT, A]))
    ].
  
  match_argument_test_() ->
    A  = arg("V"),
    AV = arg("V", 9),
    V  = arg(undefined, 9),
  