shouldFail with "unexpected result" instead of ignore

Description

Using shouldFail is a little bit tedious when it comes to having to use ignore.

In my opinion, would be nice if shouldFail could take a function that had a return value (i.e. unit -> 'a) and then use that return value in the error message if the test would fail.

Repro steps

1. Create MyTests.fs

2. Insert code:

   module MyTests
   
   open System
   open NUnit.Framework
   open FsUnitTyped
   
   [<TestCase("foo")>]
   [<TestCase("42")>] // valid int, shouldFail will trigger
   let ``Throws on invalid int`` input =
       // want to do:
       // let operation () = Convert.ToInt32 input
       let operation () = Convert.ToInt32 input |> ignore
       shouldFail operation
   
   [<Test>]
   let ``Parses int`` () =
       Convert.ToInt32 "123" |> shouldEqual 123
   

3. Run tests

Expected behavior

Error from first test should show:

 Throws on invalid int("42")
   Source: UtilityTests_Math.fs line 13
   Duration: 53 ms

  Message: 
    System.Exception : Operation did not fail.
    Unexpected result: 42
  Stack Trace: 
    TopLevelOperators.shouldFail[exn](FSharpFunc`2 f)
    UtilityTests_Math.Throws on invalid int(String input) line 13

Actual behavior

Error thrown:

 Throws on invalid int("42")
   Source: UtilityTests_Math.fs line 13
   Duration: 53 ms

  Message: 
    System.Exception : Operation did not fail.
  Stack Trace: 
    TopLevelOperators.shouldFail[exn](FSharpFunc`2 f)
    UtilityTests_Math.Throws on invalid int(String input) line 13

Related information

• Operating system: Windows
• FsUnitTyped: 2.3.2
• .NET Runtime, CoreCLR or Mono Version: .NET 4.5.1

[CaptnCodr]

@jilleJr You can close this issue. There is no plan to do it. Actually, there is no great need to use it. There are more ways to test code using other operators.

[jilleJr]

Oki ^^