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Samples for Property-based testing using FsCheck for F# and C# talk for Kiev Alt.NET
#I @".\packages\FsCheck.0.9.2.0\lib\net40-Client\"
#r @"FsCheck.dll"
// #time "on"
open FsCheck
// simple example
let revRevIsOrig (xs:list<int>) = List.rev(List.rev xs) = xs
Check.Quick revRevIsOrig;;
// unstable example
let revIsSortedOrig (xs:list<int>) = List.rev xs = List.sort xs
Check.Quick revIsSortedOrig;;
// display the counter-example
Check.Verbose revIsSortedOrig;;
// nan is one of corner cases for float type: nan <> nan
let revRevIsOrigFloat (xs:list<float>) = List.rev(List.rev xs) = xs
Check.Quick revRevIsOrigFloat;;
// grouping properties
type ListProperties =
static member ``reverse of reverse is original`` xs = revRevIsOrig xs
static member ``reverse is sorted original`` xs = revIsSortedOrig xs
Check.QuickAll<ListProperties>();;
// Conditional Properties (may take the form ==>)
let rec ordered xs =
match xs with
| [] -> true
| [x] -> true
| x::y::ys -> (x <= y) && ordered (y::ys)
let rec insert x xs =
match xs with
| [] -> [x]
| c::cs -> if x <= c then x::xs else c::(insert x cs)
let Insert (x:int) xs = ordered xs ==> ordered (insert x xs)
Check.Quick Insert;;
// Check.Verbose Insert;;
// counting trivial and classifying Test Cases
let trivialInsert (x:int) xs = ordered xs ==> ordered (insert x xs)
|> Prop.trivial (List.length xs = 0)
|> Prop.classify (ordered (x::xs)) "at-head"
|> Prop.classify (ordered (xs @ [x])) "at-tail"
|> Prop.collect (List.length xs)
Check.Quick trivialInsert;;
// forAll and integration with xUnit
Check.VerboseThrowOnFailure (Prop.forAll (Arb.Default.Int32()) (fun a b -> a + b = b + a))
Check.VerboseThrowOnFailure (Prop.forAll (Arb.Default.Int32()) (fun a b -> a + b = a + a))
//#time "off"
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