Wrong test case for Quiz1?

[A-H4NU]

  member _.``Test2-2`` () =
    let maxInt = System.Int32.MaxValue
    let result = Math.safeSub -1 maxInt
    Assert.Fail "Expected OverflowException"

As far as I know, -1 - MAX_INT does not overflow like this:

> (-1) - System.Int32.MaxValue;;
val it: int = -2147483648

Is this test case wrong?

[A-H4NU]

Someone asked this in the classroom and it was answered. :)