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Guest
Posted: Sat Sep 10, 2011 12:10 am Reply with quote
Guest
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I'm wondering how to handle testing with recursive types, especially
with regards to handling the depth at which those structures are created
in the generators.

Take, for instance, a decoded json object ({struct, [{K,V},...]} in this
case). V can obviously be a json object itself or even a list of json
objects.

I'd like to write a function is_json_object/1 that will deeply inspect a
passed json object and verify it is, in fact, a json object.

Assuming simplified types similar to:

- -type json_prop_key() :: binary().
- -type json_prop_value() :: binary() | json_object().
- -type json_object() :: {struct, [{json_prop_key(), json_prop_value()}]}.

and a function definition
- -spec is_json_object/1 :: (term()) -> boolean().
is_json_object(MaybeJObj) ->
% Implementation here
...
% return a boolean

Now, I'd like to create the PropEr tests for valid json objects. Here's
my first crack:

prop_is_json_object() ->
?FORALL(JObj, json_object_builder(),
?WHENFAIL(io:format("Failed prop_is_json_object ~p~n", [JObj]),
?MODULE:is_json_object(JObj)
)).

%% GENERATORS
%% create json objects
json_object_builder() ->
?LET(Prop, a_proplist(), {struct, Prop}).

a_proplist() ->
?SUCHTHAT(L, list( ?LET({K,V}, {binary(), proplist_value()}, {K, V})
), length(L) < 5).

proplist_value() ->
?LAZY(weighted_union([{15, binary()}, {1, json_object_builder()}])).

I tried limiting the proplist to 5 tuples, heavily weighting the
proplist_value union towards binary(), etc. When I run
"proper:module(json_tester).", I see a string of periods (varies how far
it gets), then the VM hangs and I have to get into the JCL to interrupt
the process. My assumption is that the generator is getting stuck
creating a big data structure, as CPU and memory increase rapidly.

I've looked at three examples[1][2][3] that Fred Herbert shared but
haven't found the mental bridge between his examples and my attempt. I
don't doubt that I'm misusing or ignorant of the right functions or
macros in PropEr to make this easier.

Any hints? Smile

James

[1]
https://bitbucket.org/ferd/zippers/src/9548780f0261/test/prop_zipper_lists.erl#cl-92
[2]
https://bitbucket.org/ferd/zippers/src/9548780f0261/test/prop_zipper_bintrees.erl#cl-88
[3]
https://bitbucket.org/ferd/zippers/src/9548780f0261/test/prop_zipper_forests.erl#cl-198

- --
James Aimonetti
Distributed Systems Engineer / DJ MC_

2600hz | http://2600hz.com
sip:james@2600hz.com
tel: 415.886.7905
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Guest
Posted: Sat Sep 10, 2011 2:17 am Reply with quote
Guest
James -

See the SIZED macro and resize command.

Here is an example that decrements the size for each recursive call:

type(Gen,Type) ->
?SIZED(Size,resize(if Size > 0 -> Size-1; true -> 0 end,type1(Gen,Type))).

https://github.com/norton/ubf/blob/master/test/qc/qc_ubf_types.erl

Depending on your needs, you may want to divide by 2, take the square root, etc.

thanks,

Joseph Norton


p.s. Take note - there is an open issue related to PropEr's resize implementation:

https://github.com/manopapad/proper/issues/10


On Sep 10, 2011, at 9:10 AM, James Aimonetti wrote:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> I'm wondering how to handle testing with recursive types, especially
> with regards to handling the depth at which those structures are created
> in the generators.
>
> Take, for instance, a decoded json object ({struct, [{K,V},...]} in this
> case). V can obviously be a json object itself or even a list of json
> objects.
>
> I'd like to write a function is_json_object/1 that will deeply inspect a
> passed json object and verify it is, in fact, a json object.
>
> Assuming simplified types similar to:
>
> - -type json_prop_key() :: binary().
> - -type json_prop_value() :: binary() | json_object().
> - -type json_object() :: {struct, [{json_prop_key(), json_prop_value()}]}.
>
> and a function definition
> - -spec is_json_object/1 :: (term()) -> boolean().
> is_json_object(MaybeJObj) ->
> % Implementation here
> ...
> % return a boolean
>
> Now, I'd like to create the PropEr tests for valid json objects. Here's
> my first crack:
>
> prop_is_json_object() ->
> ?FORALL(JObj, json_object_builder(),
> ?WHENFAIL(io:format("Failed prop_is_json_object ~p~n", [JObj]),
> ?MODULE:is_json_object(JObj)
> )).
>
> %% GENERATORS
> %% create json objects
> json_object_builder() ->
> ?LET(Prop, a_proplist(), {struct, Prop}).
>
> a_proplist() ->
> ?SUCHTHAT(L, list( ?LET({K,V}, {binary(), proplist_value()}, {K, V})
> ), length(L) < 5).
>
> proplist_value() ->
> ?LAZY(weighted_union([{15, binary()}, {1, json_object_builder()}])).
>
> I tried limiting the proplist to 5 tuples, heavily weighting the
> proplist_value union towards binary(), etc. When I run
> "proper:module(json_tester).", I see a string of periods (varies how far
> it gets), then the VM hangs and I have to get into the JCL to interrupt
> the process. My assumption is that the generator is getting stuck
> creating a big data structure, as CPU and memory increase rapidly.
>
> I've looked at three examples[1][2][3] that Fred Herbert shared but
> haven't found the mental bridge between his examples and my attempt. I
> don't doubt that I'm misusing or ignorant of the right functions or
> macros in PropEr to make this easier.
>
> Any hints? Smile
>
> James
>
> [1]
> https://bitbucket.org/ferd/zippers/src/9548780f0261/test/prop_zipper_lists.erl#cl-92
> [2]
> https://bitbucket.org/ferd/zippers/src/9548780f0261/test/prop_zipper_bintrees.erl#cl-88
> [3]
> https://bitbucket.org/ferd/zippers/src/9548780f0261/test/prop_zipper_forests.erl#cl-198
>
> - --
> James Aimonetti
> Distributed Systems Engineer / DJ MC_
>
> 2600hz | http://2600hz.com
> sip:james@2600hz.com
> tel: 415.886.7905
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v1.4.10 (GNU/Linux)
> Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/
>
> iQEcBAEBAgAGBQJOaqr2AAoJENc77s1OYoGgAYsH/jXoReq7uXkPxVrBvzseQULe
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> =4Srb
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> erlang-questions@erlang.org
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motiejusj
Posted: Sat Sep 10, 2011 11:45 am Reply with quote
Joined: 02 Aug 2011 Posts: 5
On Fri, Sep 09, 2011 at 05:10:30PM -0700, James Aimonetti wrote:
> I tried limiting the proplist to 5 tuples, heavily weighting the
> proplist_value union towards binary(), etc. When I run
> "proper:module(json_tester).", I see a string of periods (varies how far
> it gets), then the VM hangs and I have to get into the JCL to interrupt
> the process. My assumption is that the generator is getting stuck
> creating a big data structure, as CPU and memory increase rapidly.
>
> I've looked at three examples[1][2][3] that Fred Herbert shared but
> haven't found the mental bridge between his examples and my attempt. I
> don't doubt that I'm misusing or ignorant of the right functions or
> macros in PropEr to make this easier.
>
> Any hints? Smile
>

You can limit recursion depth as well. Just pass max_size to the
proper:quickcheck() function. That helped me as I didn't have to write
my own recursive generator. Smile

As the topic is quite similar, I would like to remind about creating
custom types in PropEr.
http://erlang.org/pipermail/erlang-questions/2011-August/060619.html

Thanks

Motiejus
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Guest
Posted: Sat Sep 10, 2011 1:06 pm Reply with quote
Guest
On 09/10/11 14:46, Motiejus Jak
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Guest
Posted: Sat Sep 10, 2011 8:25 pm Reply with quote
Guest
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On 09/10/2011 06:06 AM, Kostis Sagonas wrote:
> On 09/10/11 14:46, Motiejus Jak
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