first approach to property-based testing

test/jiffy_SUITE.erl

@@ -0,0 +1,25 @@
+-module(jiffy_SUITE).
+-include_lib("proper/include/proper.hrl").
+-include_lib("proper_stdlib/include/proper_ct.hrl").
+-compile(export_all).
+
+all() -> proper_ct:testcases(?MODULE).
+
+init_per_testcase(tc_prop_foo, Config) ->
+     [{proper, [{numtests, 1000}]} | Config].
+
+-type json_any()    :: json_list()
+                     | json_dict()
+                     | json_number()
+                     | json_string()
+                     | json_null().
+-type json_list()   :: list(json_any()).
+-type json_dict()   :: {[{json_key(), json_any()}]}.
+-type json_key()    :: binary().
+-type json_number() :: integer() | float().
+-type json_string() :: binary().
+-type json_null()   :: null.
+
+prop_foo() ->
+    ?FORALL(Data, json_any(),
+            Data == jiffy:decode(jiffy:encode(Data))).