[erlang-questions] PropEr after test clean up

Hynek Vychodil <>
Mon May 25 18:45:08 CEST 2015


There is commit showing how ugly is resulting code
https://github.com/pichi/erlgt/commit/47aa088658ca6ca1e39e9630cd188f46e685e27a

On Mon, May 25, 2015 at 6:40 PM, Hynek Vychodil <>
wrote:

> It is exactly how I discovered this behaviour. See
> https://github.com/pichi/erlgt/blob/ff3249893464f19765c74db2eae24273f15f66fd/src/gen_digraph.erl#L153
>
> When I implemented otp_digraph as a wrapper for digraph module from stdlib
> I realised it doesn't work.
>
> On Mon, May 25, 2015 at 6:34 PM, Erik Søe Sørensen <>
> wrote:
>
>> Would a try...after...end be any help?
>> Den 25/05/2015 17.11 skrev "Hynek Vychodil" <>:
>>
>>> Hi,
>>>
>>> I bumped in the problem how clean up after property in PropEr. Let's
>>> have simple property where I make ets table:
>>>
>>> prop_ets() ->
>>>     ?FORALL(V, integer(),
>>>         begin
>>>             E = ets:new(),
>>>             true = ets:insert(T, {V, ok}),
>>>             equals([{V, ok}], ets:lookup(T, V))
>>>         end
>>>     ).
>>>
>>> How am I supposed to delete ets table? It is trickier than looks like.
>>> The problem is when I want use another ?FORALL inside my property. The
>>> conjunction/1 is the same problem. You can`t write
>>>
>>> prop_ets() ->
>>>     ?FORALL(V, integer(),
>>>         begin
>>>             E = ets:new(),
>>>             true = ets:insert(T, {V, ok}),
>>>             Res = conjunction([{lookup, equals([{V, ok}], ets:lookup(T,
>>> V))},
>>>                               {lookup_element,
>>> equals(ok, ets:lookup_element(T, V, 2))}]),
>>>             ets:delete(T),
>>>             Res
>>>         end
>>>     ).
>>>
>>> Because Res is test(). In this case, you can make calls to
>>> the ets:lookup/2 and the ets:lookup_element/3 before conjunction/1 but it
>>> doesn't solve properties like
>>>
>>> ?FORALL(L, list(...),
>>>     begin
>>>         T = ets:new(),
>>>         ...
>>>         ?FORALL(V, oneof(L),
>>>               ...
>>>         )
>>>      end
>>> )
>>>
>>> The solution would be simple is every test case would be run in a
>>> separate process, but it is not! It is very unusual in Erlang word to make
>>> such thing. Processes are cheap and I can they are in a defined state each
>>> run for free. Why is it all running in the same process?
>>>
>>> Has anybody solved this problem somehouw?
>>>
>>> Hynek Vychodil
>>>
>>> _______________________________________________
>>> erlang-questions mailing list
>>> 
>>> http://erlang.org/mailman/listinfo/erlang-questions
>>>
>>>
>
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