Typically you don't write test.check generators like this. You'll build up
a generator using the test.check generator combinators. You can see some
examples of this in the
documentation: https://github.com/clojure/test.check/blob/master/doc/intro.md.
Reid
On Wednesday, December 10, 2014 12:22:18 AM UTC-6, cliff wrote:
>
> Nico, what is the correct way to turn my function which generates the
> graph (using core.logic) into a generator?
>
>
> On Monday, 8 December 2014 09:04:14 UTC+2, cliff wrote:
>>
>> Hi
>>
>> I would like to test a function which recursively traverses the nodes in
>> a graph and collects them. For example,
>>
>> (def graph {1 [2 3 4]
>> 2 [5 6 7]
>> 6 [8 9]
>> 10 [11 12 13]}
>>
>> my function is given a starting point say, 1 and should then traverse
>> each node which is reachable and return the set. In this case the result
>> should be:
>> #{3, 4, 5, 7, 8, 9}
>>
>> note: it does not return any elements reachable by 10.
>>
>> I would like to test this using test.check, but I would like to generate
>> test data which will exercise the traversal of the graph.
>>
>> I found a similar thread here:
>> https://groups.google.com/forum/#!topic/clojure/YWeT8BFc8k4
>>
>> But, I don't think the proposed solution would suit this use case. So, I
>> tried generating a graph with relations using core.logic
>>
>> (defn ->maps
>>>
>>> "take the output of run* and convert it into sequence of maps"
>>> [q]
>>> (let [r (->> q
>>> (partition 2)
>>> (map (fn [[k v]] {k (apply vector v)}))
>>> (apply merge))]
>>> r ))
>>> (defn gen-hierarchy
>>> "generate a related hierarchy"
>>> [size]
>>> (let [vars1 (->> (repeatedly 7 lvar) (into []))
>>> vars2 (->> (repeatedly 7 lvar) (into []))
>>> vars3 (->> (repeatedly 7 lvar) (into []))]
>>> (->>
>>> (run size [q]
>>> (fresh [?k1 ?k2 ?k3 ?v1 ?v2 ?v3 ?a]
>>> (fd/distinct vars1)
>>> (everyg #(fd/in % (fd/interval 1 9)) vars1)
>>> (fd/in ?k1 (fd/interval 1 9))
>>> (rembero ?k1 vars1 ?v1)
>>> (membero ?k2 ?v1)
>>> (fd/distinct vars2)
>>> (everyg #(fd/in % (fd/interval 1 9)) vars2)
>>> (rembero ?k2 vars2 ?v2)
>>> (membero ?k3 ?v2)
>>> (fd/distinct vars3)
>>> (everyg #(fd/in % (fd/interval 1 9)) vars3)
>>> (rembero ?k3 vars3 ?v3)
>>> (appendo [?k1 ?v1] [?k2 ?v2] ?a)
>>> (appendo ?a [?k3 ?v3] q)))
>>> (map ->maps))))
>>>
>>>
>> Hooking this into test.check. I tried the following:
>>
>> (defn gen-port-hierarchy []
>>> (gen/sized (fn [size]
>>> (gen/fmap #(gen-hierarchy %) (gen/return size)))))
>>> (gen/sample (gen/not-empty (gen-port-hierarchy)) 1)
>>
>>
>> Which does produce more or less what I'm after:
>>
>> (({6 [2 3 4 5 7 1], 3 [6 7 1 2 4 5], 1 [3 2 4 5 6 7]})
>> ({5 [1 2 3 4 6 7], 7 [5 3 4 6 1 2], 1 [7 2 3 4 5 6]}))
>>
>> However, when I try use this in a spec:
>>
>> (prop/for-all [bindings (gen/not-empty (gen-port-hierarchy))]
>>
>> (let [ ks (into #{} (keys bindings))] ...)
>>
>>
>> I seem to be getting back a LazySeq which then leads to a
>> ClassCastException:
>>
>> java.lang.ClassCastException: clojure.lang.PersistentArrayMap cannot be
>> cast to java.util.Map$Entry
>>
>> Am I on the completely wrong path here?
>> Or have I incorrectly hooked this generator up with test.check?
>>
>> Any help would be very appreciated.
>>
>>
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