c# - 如何使用应有的自定义断言并维护特定于调用站点的断言消息？

Question

我正在使用 the excellent Shouldly library在我的 xUnit 测试中，我发现自己在不同的测试中使用了断言的集合序列，所以我将它们组合成新的断言扩展方法 - 但是当我这样做时，我丢失了 Shouldly的上下文断言消息。

这是我的旧代码，适用于 Shouldly在 Shouldly 中包含源级信息和调用站点上下文断言错误:

[Fact]
public void Dict_should_contain_valid_Foobar_Bar_entry()
{
    IDictionary<String,Bar> dict = ...
    dict.TryGetValue( "Foobar", out Bar bar ).ShouldBeTrue();
    bar.ShouldNotBeNull();
    bar.ChildList.Count.ShouldBe( expected: 3 );
    bar.Message.ShouldBeNull();
}

[Fact]
public void Dict_should_contain_valid_Barbaz_Bar_entry()
{
    IDictionary<String,Bar> dict = ...
    dict.TryGetValue( "Barbaz", out Bar bar ).ShouldBeTrue();
    bar.ShouldNotBeNull();
    bar.ChildList.Count.ShouldBe( expected: 3 );
    bar.Message.ShouldBeNull();
}

我在同一个项目中将它转换为这个新的扩展方法:

public static void ShouldBeValidBar( this IDictionary<String,Bar> dict, String barName )
{
    dict.ShouldNotBeNull();
    dict.TryGetValue( barName, out Bar bar ).ShouldBeTrue();
    bar.ShouldNotBeNull();
    bar.ChildList.Count.ShouldBe( expected: 3 );
    bar.Message.ShouldBeNull();
}

所以我的测试变成了这样:

[Fact]
public void Dict_should_contain_valid_Foobar_Bar_entry()
{
    IDictionary<String,Bar> dict = ...
    dict.ShouldBeValidBar( "Foobar" );
}

[Fact]
public void Dict_should_contain_valid_Barbaz_Bar_entry()
{
    IDictionary<String,Bar> dict = ...
    dict.ShouldBeValidBar( "Barbaz" );
}

...但现在我的应该断言消息不包含来自 Dict_should_contain_valid_Foobar_Bar_entry 的任何上下文信息而是只包含来自 ShouldBeValidBar 的上下文.

如何指导Shouldly忽略 ShouldBeValidBar 的上下文并改用其父调用站点？

Answer 1

特尔；博士:

添加 [ShouldlyMethods]属性到您的自定义断言扩展方法 类(class) (不是单独的扩展方法):

[ShouldlyMethods] // <-- This, right here!
public static class MyShouldlyAssertions
{
    public static void ShouldBeValidBar( this IDictionary<String,Bar> dict, String barName )
    {
        [...]
    }
}

长版:

经过一番谷歌搜索，and reading articles about how Shouldly works - 阅读后the source of Shouldly's secret-sauce: SourceCodeTextGetter ，我看到它决定了堆栈跟踪中的哪些条目可以忽略 by the presence of the [ShouldlyMethods] attribute ( Shouldly.ShouldlyMethodsAttribute ) 在堆栈跟踪的每一帧中的方法包含类型:

void ParseStackTrace(StackTrace trace)
{
    [...]

    while (ShouldlyFrame == null || currentFrame.GetMethod().IsShouldlyMethod())
    {
        if (currentFrame.GetMethod().IsShouldlyMethod())
            ShouldlyFrame = currentFrame;

        [...]
    }

    [...]
}

internal static bool IsShouldlyMethod(this MethodBase method)
{
    if (method.DeclaringType == null)
        return false;

    return
        method
            .DeclaringType
            .GetCustomAttributes( typeof(ShouldlyMethodsAttribute), true )
            .Any()
        ||
        (
            method.DeclaringType.DeclaringType != null
            && 
            method
                .DeclaringType
                .DeclaringType
                .GetCustomAttributes( typeof(ShouldlyMethodsAttribute), true )
                .Any()
        );
}

所以只需添加 [ShouldlyMethods]属性到我的扩展方法的容器类:

[ShouldlyMethods]
public static class ShouldlyAssertionExtensions
{    
    public static void ShouldBeValidBar( this IDictionary<String,Bar> dict, String barName )
    {
        dict.ShouldNotBeNull();
        dict.TryGetValue( barName, out Bar bar ).ShouldBeTrue();
        bar.ShouldNotBeNull();
        bar.ChildList.Count.ShouldBe( expected: 3 );
        bar.Message.ShouldBeNull();
    }
}

现在我的断言错误具有 ShouldBeValidBar 的调用站点的上下文.欢呼!