如何使用FsUnit正确测试异常 [英] How to properly test Exceptions with FsUnit

问题描述

我正在尝试找出如何使用FsUnit正确测试异常的方法.官方文档指出，要测试例外情况，我必须纠正以下内容:

I'm trying to figure out how to properly test exceptions with FsUnit. Official documentation states, that to test for exceptions I have to right something like this:

(fun () -> failwith "BOOM!" |> ignore) |> should throw typeof<System.Exception>

但是，如果我不使用[<ExpectedException>]属性标记测试方法，它将始终失败.听起来很合理，因为如果我们要测试异常，则必须在C#+ NUnit中添加此类属性.

But, if I don't mark my test method with [<ExpectedException>] attribute it will always fail. Sounds reasonable because if we want to test for exceptions we have to add such attribute in C# + NUnit.

但是，只要我添加了此属性，无论我尝试引发哪种异常都无所谓，它将始终得到处理.

But, as long as I've added this attribute it doesn't matter what kind of exception I'm trying to throw, it will be always handled.

一些摘要: 我的LogicModule.fs

Some snippets: My LogicModule.fs

exception EmptyStringException of string

let getNumber str =
    if str = "" then raise (EmptyStringException("Can not extract number from empty string"))
    else int str

我的LogicModuleTest.fs

My LogicModuleTest.fs

[<Test>]
[<ExpectedException>]
let``check exception``()=
    (getNumber "") |> should throw typeof<LogicModule.EmptyStringException>

推荐答案

已找到答案.要测试是否引发了异常，我应该使用下一种样式包装函数调用:

Answer has been found. To test that exception was thrown I should wrap my function call in the next style:

(fun () -> getNumber "" |> ignore) |> should throw typeof<LogicModule.EmptyStringException>

因为在#fsunit下面使用了NUnit的Throws约束 http://www.nunit.org/index.php?p=throwsConstraint&r=2.5 …需要一个void的代表，raise返回'a

because underneath #fsunit uses NUnit's Throws constraint http://www.nunit.org/index.php?p=throwsConstraint&r=2.5 … which takes a delegate of void, raise returns 'a

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