Test if the behaviour of two functions are the same.

gistfile1.fs

// Some dummy data types
type Thing = Red | Yellow | Blue
type Foo = { Number : PositiveInt; Other : Thing }

/// First way
let groupByThenSortAndHead data =
    data
    |> Array.groupBy(fun x -> x.Other)
    |> Array.map (
        snd
        >> Seq.sortByDescending(fun x -> x.Number)
        >> Seq.head)

/// Second way
let sortThenDistinct data =
    data
    |> Array.sortByDescending(fun x -> x.Number)
    |> Array.distinctBy(fun x -> x.Other)

/// Create a "test" function which returns true or false if some property holds.
let bothMethodsAreTheSame data =
    groupByThenSortAndHead data = sortThenDistinct data

/// FsCheck tests the compareThem function with random data
Check.Quick bothMethodsAreTheSame