pos-int? is equivalent to [:int {:min 1}] Type schemas are more flexible than predicate schemas

You can then add upper boundary with no complications

Excellent thanks! This is what I was looking for [:int {:min 0 :gen/max 10}] ; i.e. eq to nat-int? for validation and [0,10] for the generated range

yep

Where types are concerned, I prefer the type schemas (with keywords) and not the predicate schemas

You use case is a perfect example why

Use a set generator then fmap vec

Great thanks! Although this has been a little bit of a mouthful it has done the trick:

[:vector {:min 400 
          :gen/schema [:set {:min 10} string?]
          :gen/fmap vec} 
         string?]

(perhaps there should be a :gen/distinct option for collections? clojure.test.check.generators does seem to provide list-distinct and`vector-distinct` to this end)

This unfortunately does not scale very well, because I'd need to repeat the vector predicate twice, one for :vector the other for the generator's schema, which could easily get out of sync for more complicated schemas, e.g.

[:vector {:min 400
          :gen/schema [:set {:min 10} [:map [:x int?] [:y string?]]]
          :gen/fmap vec
         }
         [:map [:x int?] [:y string?]]]

At that point you might want to define your own type and use a registry, you could call it distinct vector. Why does it need to be a vector, btw? Why can't it be. a set?

Hi, it has to be a vector because this is how values are coming out from the data source. The distinct values are only needed by the generator to produce some specific values during testing only. I can't seem to create a custom type with -simple-schema for distinct-vector ... The syntax of the type looks to be in accordance with the section on the readme file, but it gives me a :malli.core/invalid-schema {:schema (#object[cljs$core$string_QMARK_])} error when I try to use it ...

(let [vector-distinct
      (malli.core/-simple-schema
        (fn [_ schema]
          (let [schema (first schema)])
          {:type :vector-distinct
           :pred vector?
           :type-properties
           {:gen/gen (clojure.test.check.generators/vector-distinct (malli.generator/generator schema))}}))]
  (-> [vector-distinct {} string?]
      malli.generator/generate))

I think you want a variation on vector-of

the schema itself is incorrect, not the generation

sorry, not sure what you mean by "a variation on vector-of"; but I think I got it this time working, It appears I was missing the number of arguments accepted by the new type, in my case 1 (as in :min and :max):

(let [vector-distinct
        (malli.core/-simple-schema
         (fn [_ schema]
           (let [schema (first schema)]
             {:type ::vector-distinct
              :min 1
              :max 1
              :pred vector?
              :type-properties
              {:gen/gen (clojure.test.check.generators/vector-distinct (malli.generator/generator schema))}})))]
    (->> [vector-distinct string?]
        malli.generator/generate))

Actually that is not complete because pred is not going to check the vector values for conformity. I will stick with the following hack which almost does what I want (the only glitch is that generated distinct values are likely to be less than :min):

[:vector {:min 400 :max 400
          :gen/fmap #(into [] (set %))} string?]

ah, you need a collection schema, that's it