使用FsUnit.Xunit声明异常消息

Question

I'm trying to assert a certain exception type and message using FsUnit.Xunit. There is some throwWithMessage function that comes with FsUnit. However, when using it instead of the throw function fsc emits the following errors:

C:\src\foo.fs(29,12): error FS0001: This expression was expected to have type '(unit -> unit) -> 'a' but here has type 'unit' 
C:\src\foo.fs(29,19): error FS0001: The type ''a -> NHamcrest.Core.CustomMatcher<obj>' is not compatible with the type 'NHamcrest.IMatcher<obj>' 
C:\src\foo.fs(29,12): error FS0001: This expression was expected to have type '(unit -> unit) -> 'a' but here has type 'unit'

This is the test that won't compile:

[<Fact>]
let ``Some test`` () =
    (fun () -> This.Throws("a", 10) |> ignore)
    |> should throwWithMessage "Some message" typeof<ArgumentException> //This is line 29
     //^ column index 12 is here
            //^ here is column index 19

I'm not sure what's wrong here.

Versions:

• FsUnit/FsUnit.Xunit 3.1.0
• NHamcrest (as referenced by FsUnit.Xunit) 2.0.1
• Xunit 2.3.1

Answer 1

Welp, I missed some brackets. This works:

[<Fact>]
let ``Some test`` () =
    (fun () -> This.Throws("a", 10) |> ignore)
    |> should (throwWithMessage "Some message") typeof<ArgumentException>