Added basic eqc test for trunc_io:format with maxlen.

test/trunc_io_eqc.erl

@@ -0,0 +1,157 @@
+%% -------------------------------------------------------------------
+%%
+%% trunc_io_eqc: QuickCheck test for trunc_io:format with maxlen
+%%
+%% Copyright (c) 2007-2011 Basho Technologies, Inc.  All Rights Reserved.
+%%
+%% This file is provided to you under the Apache License,
+%% Version 2.0 (the "License"); you may not use this file
+%% except in compliance with the License.  You may obtain
+%% a copy of the License at
+%%
+%%   http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing,
+%% software distributed under the License is distributed on an
+%% "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+%% KIND, either express or implied.  See the License for the
+%% specific language governing permissions and limitations
+%% under the License.
+%%
+%% -------------------------------------------------------------------
+-module(trunc_io_eqc).
+
+-ifdef(TEST).
+-ifdef(EQC).
+-export([test/0, test/1, check/0]).
+
+-include_lib("eqc/include/eqc.hrl").
+-include_lib("eunit/include/eunit.hrl").
+
+-define(QC_OUT(P),
+        eqc:on_output(fun(Str, Args) -> io:format(user, Str, Args) end, P)).
+
+%%====================================================================
+%% eunit test 
+%%====================================================================
+
+eqc_test_() ->
+    {spawn, 
+     [?_assertEqual(true, quickcheck(numtests(500, ?QC_OUT(prop_format()))))]
+    }.
+
+%%====================================================================
+%% Shell helpers 
+%%====================================================================
+    
+test() ->
+    test(100).
+
+test(N) ->
+    quickcheck(numtests(N, prop_format())).
+
+check() ->
+    check(prop_format(), current_counterexample()).
+
+%%====================================================================
+%% Generators
+%%====================================================================
+
+gen_fmt_args() ->
+    list(oneof([gen_print_str(),
+                {"~p", gen_any(5)},
+                {"~w", gen_any(5)},
+                {"~s", gen_print_str()}
+               ])).
+             
+
+%% Generates a printable string
+gen_print_str() ->
+    ?LET(Xs, list(char()), [X || X <- Xs, io_lib:printable_list([X]), X /= $~]).
+
+gen_any(MaxDepth) ->
+    oneof([largeint(),
+           gen_atom(),
+           nat(),
+           binary(),
+           gen_pid(),
+           gen_port(),
+           gen_ref(),
+           gen_fun()] ++
+           [?LAZY(list(gen_any(MaxDepth - 1))) || MaxDepth /= 0] ++
+           [?LAZY(gen_tuple(gen_any(MaxDepth - 1))) || MaxDepth /= 0]).
+          
+gen_atom() ->
+    elements([abc, def, ghi]).
+
+gen_tuple(Gen) ->
+    ?LET(Xs, list(Gen), list_to_tuple(Xs)). 
+
+gen_max_len() -> %% Generate length from 3 to whatever.  Needs space for ... in output
+    ?LET(Xs, int(), 3 + abs(Xs)).
+
+gen_pid() ->
+    ?LAZY(spawn(fun() -> ok end)).
+
+gen_port() ->
+    ?LAZY(begin
+              Port = erlang:open_port({spawn, "true"}, []),
+              erlang:port_close(Port),
+              Port
+          end).
+
+gen_ref() ->
+    ?LAZY(make_ref()).
+
+gen_fun() ->
+    ?LAZY(fun() -> ok end).
+               
+%%====================================================================
+%% Property
+%%====================================================================
+    
+%% Checks that trunc_io:format produces output less than or equal to MaxLen
+prop_format() ->
+    ?FORALL({FmtArgs, MaxLen}, {gen_fmt_args(), gen_max_len()},
+            begin
+                {FmtStr, Args} = build_fmt_args(FmtArgs),
+                try
+                    Str = lists:flatten(trunc_io:format(FmtStr, Args, MaxLen)),
+                    ?WHENFAIL(begin
+                                  io:format("FmtStr: ~p\n", [FmtStr]),
+                                  io:format("Args:   ~p\n", [Args]),
+                                  io:format("MaxLen: ~p\n", [MaxLen]),
+                                  io:format("ActLen: ~p\n", [length(Str)]),
+                                  io:format("Str:    ~p\n", [Str])
+                              end,
+                              %% Make sure the result is a printable list
+                              %% and if the format string is less than the length, 
+                              %% the result string is less than the length.
+                              conjunction([{printable, Str == "" orelse 
+                                                       io_lib:printable_list(Str)},
+                                           {length, length(FmtStr) > MaxLen orelse 
+                                                    length(Str) =< MaxLen}]))
+                catch
+                    _:Err ->
+                        io:format(user, "\nException: ~p\n", [Err]),
+                        io:format("FmtStr: ~p\n", [FmtStr]),
+                        io:format("Args:   ~p\n", [Args]),
+                        false
+                end
+            end).
+
+%%====================================================================
+%% Internal helpers 
+%%====================================================================
+
+%% Build a tuple of {Fmt, Args} from a gen_fmt_args() return
+build_fmt_args(FmtArgs) ->
+    F = fun({Fmt, Arg}, {FmtStr0, Args0}) ->
+                {FmtStr0 ++ Fmt, Args0 ++ [Arg]};
+           (Str, {FmtStr0, Args0}) ->
+                {FmtStr0 ++ Str, Args0}
+        end,
+    lists:foldl(F, {"", []}, FmtArgs).
+
+-endif. % (TEST).
+-endif. % (EQC).