Details
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Type:
Enhancement
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Status:
Open
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Priority:
Minor
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Resolution: Unresolved
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Affects Version/s: None
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Fix Version/s: None
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Component/s: None
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Labels:None
Description
I'm working through some of the examples in John Hughes' "QuickCheck Testing for Fun and Profit" paper. I'd like the structures I generate in those tests to look like the this:
[:apply `reg [(gen-name) (gen/elements pids)]]
Rather than the way they must be expressed now:
(gen/tuple (gen/return :apply) (gen/return `reg) (gen/tuple (gen-name) (gen/elements pids)))
I think a simple recursive function could be used to generate these, with the caveat that currently generators create a map {:gen #<fn...>}, which I'd propose to change to a record so that we could distinguish between a generator and a map data-structure.
This seems to be implemented to good effect in Quvig QuickCheck already:
In general, Quviq QuickCheck permits any data-structure containing embedded generators to be used as a generator for data-structures of that shape—something which is very convenient for users, but quite impossible in Haskell, where embedding a generator in a data-structure would normally result in a type error. This technique is used throughout the generators written at Ericsson. – Hughes
Playing around in the REPL today, I came up with this code that seems to work well converting arbitrary literals into generators:
(defprotocol LiteralGenerator (-literal->generator [literal])) (defn literal->generator [literal] (cond (satisfies? LiteralGenerator literal) (-literal->generator literal) (vector? literal) (apply gen/tuple (mapv literal->generator literal)) (and (map? literal) (= [:gen] (keys literal)) (fn? (:gen literal))) literal (map? literal) (gen/fmap (partial into {}) (literal->generator (mapv vec literal))) (set? literal) (gen/fmap set (literal->generator (vec literal))) (list? literal) (gen/fmap (partial apply list) (literal->generator (vec literal))) :else (gen/return literal)))Generating from a record is probably something that would be generally useful, so I added this as well:
Which enables me to extend a record like this:
I haven't looked at the possibility of baking this code into test.check at all yet. I'd like feedback on what I've got so far before pursuing this any further.
(defprotocol LiteralGenerator (-literal->generator [literal])) (defn literal->generator [literal] (cond (satisfies? LiteralGenerator literal) (-literal->generator literal) (vector? literal) (apply gen/tuple (mapv literal->generator literal)) (and (map? literal) (= [:gen] (keys literal)) (fn? (:gen literal))) literal (map? literal) (gen/fmap (partial into {}) (literal->generator (mapv vec literal))) (set? literal) (gen/fmap set (literal->generator (vec literal))) (list? literal) (gen/fmap (partial apply list) (literal->generator (vec literal))) :else (gen/return literal)))