F# test if the result is Some(any)

Question

I need to check whether my validation function returns something when fails or none. If it returns Some<string>, there is a validation error, otherwise it's valid and the function returns None. This is my attempt , but it's not refactoring safe:

[<Property(Arbitrary=[| typeof<Strings.WithLenFrom1To100> |])>]
    let ``lengthValidator should return some error when the string's length is longer than expected``(str:string)=
        let maxValidLen = str.Length-1
        let actual = lengthValidator maxValidLen str

        let expected = Some(sprintf "Maximum string length is %i but %s contains %i characters" maxValidLen str str.Length)
        //How can I say **let expected = Some(anything) **instead

        test <@actual = expected@>

Answer 1

test <@ actual.IsSome @>