F# Factory With Type Inference

Tests.fs

module Tests

open Xunit

type Factory<'T> = unit -> 'T

let factoryFunction<'T> () : 'T =
    if typeof<'T> = typeof<string> then "String" :> obj
    elif typeof<'T> = typeof<int> then 1 :> obj
    else failwith "Unsupported type"
    |> unbox<'T>

[<Fact>]
let ``Can Factory 5`` () =
    let factory : Factory<_> = factoryFunction

    // Create a string
    let testString = factory()
    Assert.Equal("String", testString)

    // Create an int
    let testInt = factory()
    Assert.Equal(1, testInt)