anchor.diff:  let testIters = 10
   let x = 1000UL
   let testLen = 1000000
  -let r = System.Random()
  +let rand = System.Random()
   
   let compareByElems (bra : BlockResizeArray<'T>) (arr : 'T []) = 
       let mutable res = true 
  
positive.code:     let braRes = bra.Fold (fun acc elem -> acc + elem) 0
      Assert.AreEqual(braRes, aRes) 
  
  let createRandBra count =
      let rand = System.Random()
      BlockResizeArray.Init count (fun i -> rand.Next())
  
  type ArbitraryModifiers =    
      static member BlockResizeArray() = 
          Arb.generate<int> 
          |> Gen.suchThat (fun i -> i >= 0)
          |> Gen.map (fun i -> createRandBra (i * 10000))
          |> Arb.fromGen
  
  [<SetUp>]
  
negative.code:         let b = bra.Map f
          let a = Array.map f arr
          compareByElems b a
      Check.VerboseThrowOnFailure <| testFun (fun e -> e * 2)
      
  [<Test>]
  let ``Random filter``() =   
  