Helpers.elm

module Helpers exposing (exprFuzzer)

import Fuzz exposing (Fuzzer)


exprFuzzer :
    { baseCases : List (Fuzzer a)
    , recursiveCases : Fuzzer a -> List (Fuzzer a)
    , maxDepth : Int
    }
    -> Fuzzer a
exprFuzzer config =
    Fuzz.oneOf <|
        if config.maxDepth <= 0 then
            config.baseCases

        else
            config.baseCases
                ++ config.recursiveCases (exprFuzzer { config | maxDepth = config.maxDepth - 1 })

Tests.elm

symbolicFuzzer : Fuzzer Symbolic
symbolicFuzzer =
    Helpers.exprFuzzer
        { baseCases = baseCases
        , recursiveCases = recursiveCases
        , maxDepth = 3
        }


baseCases : List (Fuzzer Symbolic)
baseCases =
    [ Fuzz.map S.num Fuzz.niceFloat
    , Fuzz.map S.var letterFuzzer
    ]


recursiveCases : Fuzzer Symbolic -> List (Fuzzer Symbolic)
recursiveCases recur =
    [ Fuzz.map2 S.add recur recur
    , Fuzz.map2 S.mul recur recur
    , Fuzz.map2 S.pow recur recur
    ]