Some good links here: https://github.com/clojure/test.check
But related communities like QuickCheck, ScalaCheck, etc are probably good places to look. Someone should start making something great for test.check on the wiki: https://github.com/clojure/test.check Hint hint hint! On Wednesday, April 30, 2014 3:10:34 PM UTC-5, Tim Visher wrote: > > As an aside to the discussion at hand, what papers/books/online > articles are good to read to learn about how to come up with good > properties and generators? > > On Wed, Apr 30, 2014 at 3:36 PM, Alex Miller > <al...@puredanger.com<javascript:>> > wrote: > > The only hard parts about property based testing are the properties and > the > > generators. ;) > > > > On Wednesday, April 30, 2014 6:38:19 AM UTC-5, henry w wrote: > >> > >> Hi, I wanted to get started with clojure.test.check (formerly > >> simple-check) and I am new to property based testing. > >> > >> I plucked clojure.core/group-by for no particular reason as a function > to > >> test. > >> > >> I started by stating some properties i think should hold: > >> > >> ;; 1. applying the grouping key function to each member in a grouping > >> should result in the grouping key > >> ;; 2. flattening the vals of the group-by result should give back the > >> contents of the original collection. > >> ;; 3. no element appears in more than one grouping. > > > > > > those seem good > > > >> > >> > >> so far so good I think. there may be others but this seems ok for now. > >> > >> now, how to generate some data. > >> > >> for group-by we need two params: > >> 1) a grouping function > >> 2) a collection of items to be grouped > >> > >> If I start by naively generating collections of maps (containing > keyword > >> keys and int vals, for example), the data is of the right shape to use > in > >> group by, but there is no guarantee that: > >> 1) any of the maps share a key that I could use for grouping > >> 2) the values under a common key are shared > >> > >> This is really the crux of my problem.... ideally I would have the > >> generator *mostly* produce data which is actually doing to result in > the > >> sort of collection i might want to call group-by on in real life (ie > not > >> have everything grouped under nil on each generation). So should i > create a > >> generator that creates keywords (which i will want to use as grouping > >> function) then have another generator that produces what are going to > be the > >> values under this grouping key, then a generator that uses both of > these to > >> create collections of maps from these. then i would have to find out > what > >> the grouping keyword was that was generated.... this could all work, I > have > >> read enough about generators to have a stab at this... but is it the > right > >> approach? > > > > > > You don't seem to be leveraging the possibilities of the grouping > function. > > If you create a grouping function that maps many random values into a > small > > number of groups, then everything may get easier. Some candidate > functions: > > first character of the keyword, length of the keyword, etc. > > > > Or working backwards is often useful with a generator - generate the > > grouping values first, then use the inverse of the grouping function to > > generate data that maps to that group and populate the input with that. > > > >> > >> > >> as far as implementing tests for the properties so far, I have done > >> property 2 above, using a basic generator and yanking out an arbitrary > key > >> from it.... clearly a flawed approach as not much 'realistic' grouping > is > >> going to happen here. > >> > >> (def vector-of-maps (gen/such-that not-empty (gen/vector (gen/such-that > >> not-empty (gen/map gen/keyword gen/int))))) > >> > >> (def all-elements-are-grouped > >> (prop/for-all [group-by-input vector-of-maps] > >> (let [a-map-key (-> group-by-input first keys first)] > ;; > >> hmm, seems far from ideal > >> (= (set group-by-input) (-> (group-by a-map-key > >> group-by-input) vals flatten set))))) > >> > >> help appreciated... perhaps I need to learn more about the paradigm > first, > >> but resources linked from the readme are all a bit more basic than > this. so > >> if you know of some more advanced tutorials please let me know. > >> > >> Thanks > > > > -- > > You received this message because you are subscribed to the Google > > Groups "Clojure" group. > > To post to this group, send email to clo...@googlegroups.com<javascript:> > > Note that posts from new members are moderated - please be patient with > your > > first post. > > To unsubscribe from this group, send email to > > clojure+u...@googlegroups.com <javascript:> > > For more options, visit this group at > > http://groups.google.com/group/clojure?hl=en > > --- > > You received this message because you are subscribed to the Google > Groups > > "Clojure" group. > > To unsubscribe from this group and stop receiving emails from it, send > an > > email to clojure+u...@googlegroups.com <javascript:>. > > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
