FsCheck function to generate Japanese characters.

gistfile1.fs

namespace FsCheck.Ext
 
module Test =
    open System
    open FsCheck
    open FsCheck.Arb

    type JapaneseChar = char
    
    let japaneseChar (s: string) : JapaneseChar =
        char s
 
    type MyGenerators =
        static member JapaneseChar() =
            { new Arbitrary<JapaneseChar>() with
                override x.Generator = Gen.oneof [
                                        Gen.choose(0x3000, 0x303f) |> Gen.map (Char.ConvertFromUtf32 >> japaneseChar)
                                        Gen.choose(0x3040, 0x309f) |> Gen.map (Char.ConvertFromUtf32 >> japaneseChar)
                                        ]
            }
 
 
    let sample n = Gen.sample 1000 n
 
    type Target() =
        static member JapaneseChar (value:JapaneseChar) =
            (generate<JapaneseChar> |> sample 10 |> List.forall (fun _ -> true)
            , shrink<JapaneseChar> value |> Seq.forall (fun shrunkv -> int shrunkv <= abs (int value)))

    // Here I registered my own Arbitrary, but it doesn't work correctly at the first time
    Arb.register<MyGenerators>() |> ignore
    Check.QuickAll<Target>()
    
    // Register again *after running QuickAll*.
    // This time QuickAll works fine.
    Arb.register<MyGenerators>() |> ignore
    Check.QuickAll<Target>()

gistfile2.txt

--- Checking Target ---
Target.JapaneseChar-Falsifiable, after 1 test (0 shrinks) (StdGen (1898206864,295898127)):
'\004'

--- Checking Target ---
Target.JapaneseChar-Ok, passed 100 tests.

Variation:

    Check.QuickAll<Target>() // Doesn't work (but it's OK because I don't register my own Arbitrary yet)
    Arb.register<MyGenerators>() |> ignore
    Check.QuickAll<Target>() // Works fine

    Arb.register<MyGenerators>() |> ignore
    Arb.register<MyGenerators>() |> ignore
    Check.QuickAll<Target>() // Desn't work