[英]How to test whether a ref struct method is throwing an exception using xUnit?
I'm new to xUnit, but, as far as I know, the standard way of checking whether something throws an exception is to use Assert.Throws<T>
or Assert.ThrowsAny<T>
methods. 我是xUnit的新手,但据我所知,检查是否抛出异常的标准方法是使用
Assert.Throws<T>
或Assert.ThrowsAny<T>
方法。
But these methods expect an Action as parameter; 但是这些方法期望将Action作为参数; and ref structs can't be "embedded" in lambdas.
并且ref结构不能“嵌入”lambda中。
So, how does one test whether a given method of a ref struct is throwing? 那么,如何测试ref struct的给定方法是否抛出? Example of code that doesn't work:
不起作用的代码示例:
[Fact]
public void HelpMe() {
var pls = new Span<byte>();
Assert.ThrowsAny<Exception>(() => {
plsExplode = pls[-1];
});
}
A ref struct can't be captured in a lambda expression, but you can still use it in a lambda expression - you just need to declare the variable there, so that it's never a field within a non-ref-struct. 无法在lambda表达式中捕获 ref结构,但您仍然可以在lambda表达式中使用它 - 您只需要在那里声明变量,这样它就不会是非ref-struct中的字段。
For example, this compiles and succeeds: 例如,这会编译并成功:
[Fact]
public void HelpMe()
{
Assert.ThrowsAny<Exception>(() => {
var pls = new Span<byte>();
var plsExplode = pls[-1];
});
}
Now I'll be the first to admit that this isn't ideal: you really want to do the minimum amount of work possible within the action, so that you only pass if the expected piece of code fails. 现在我将是第一个承认这不理想的人:你真的想在动作中尽可能少地完成工作,这样你只有在预期的代码段失败时才会通过。
Using Assert.Throws
helps there, so that only the expected exception results in a pass. 使用
Assert.Throws
帮助,因此只有预期的异常会导致传递。 Additionally, you could capture a bool
which is changed just before the throwing part, then check that you'd got that far: 另外,你可以捕获一个在投掷部分之前改变的
bool
,然后检查你是否已经达到了这个目的:
[Fact]
public void HelpMe()
{
bool reachedThrowingPart = false;
Assert.Throws<IndexOutOfRangeException>(() =>
{
var span = new Span<byte>();
reachedThrowingPart = true;
var ignored = span[-1];
});
Assert.True(reachedThrowingPart);
}
It's all significantly wordier than it would be if it weren't for ref struct restrictions, but they're understandable... 如果它不是用于reftruct限制的话,它会显得更加冗长,但它们是可以理解的......
You could implement your own Assert.Throws
that passes the ref struct
through a parameter to avoid capturing it in a closure. 您可以实现自己的
Assert.Throws
,它通过参数传递ref struct
,以避免在闭包中捕获它。
using System;
using Xunit;
public ref struct RefStruct1
{
public void MethodThatThrows(int x) => throw new NotImplementedException();
}
public class Test1
{
[Theory]
[InlineData(0)]
[InlineData(int.MaxValue)]
public void MethodThatThrows_Always_ThrowsNotImplementedException(int x)
{
var refStruct1 = new RefStruct1();
AssertThrows<NotImplementedException>(ref refStruct1, (ref RefStruct1 rs1) => rs1.MethodThatThrows(x));
}
private delegate void RefStruct1Action(ref RefStruct1 rs1);
[System.Diagnostics.DebuggerStepThrough]
private static T AssertThrows<T>(ref RefStruct1 rs1, RefStruct1Action action)
where T : Exception
{
if (action == null)
throw new ArgumentNullException(nameof(action));
try
{
action(ref rs1);
}
catch (Exception ex)
{
if (ex.GetType() == typeof(T))
return (T)ex;
throw new Xunit.Sdk.ThrowsException(typeof(T), ex);
}
throw new Xunit.Sdk.ThrowsException(typeof(T));
}
}
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