Randomly repeat characters in a string

repeatChars.fs

test
            "repeated characters are replaced with one"
            {
                let randomlyRepeat char =
                    gen {
                        let! randomLength = Arb.generate<int> |> Gen.map (fun i -> abs i + 1)
                        return String(char, randomLength)
                    }
                    
                let arbitrarilyRepeatCharactersInString s =
                    gen {
                        let! result =
                            Seq.map randomlyRepeat s
                            |> Gen.sequence
                        let single = String.concat "" result
                        return single
                    }
                    
                let cases = gen {
                    let! r = randomString
                    let! repeated = arbitrarilyRepeatCharactersInString r
                    return (r, repeated)
                }
                
                let c = Gen.sample 10 100 cases
                Tests.failtest "OMG I failed!"
             }