模拟扩展方法导致 System.NotSupportedException [英] Mocking of extension method result in System.NotSupportedException
问题描述
我正在对使用 IMemoryCache
接口的 ClientService 进行单元测试:
I'm unit testing a ClientService that uses the IMemoryCache
interface:
ClientService.cs:
ClientService.cs:
public string Foo()
{
//... code
_memoryCache.Set("MyKey", "SomeValue", new TimeSpan(0, 0, 60));
}
当我尝试模拟 IMemoryCache
的 Set
扩展时:
When I try to mock the IMemoryCache
's Set
extension with:
AutoMock mock = AutoMock.GetLoose();
var memoryCacheMock = _mock.Mock<IMemoryCache>();
string value = string.Empty;
// Attempt #1:
memoryCacheMock
.Setup(x => x.Set<string>(It.IsAny<object>(), It.IsAny<string>(), It.IsAny<TimeSpan>()))
.Returns("");
// Attempt #2:
memoryCacheMock
.Setup(x => x.Set(It.IsAny<object>(), It.IsAny<object>(), It.IsAny<TimeSpan>()))
.Returns(new object());
它抛出一个异常:
System.NotSupportedException:不支持的表达式:x =>x.Set(It.IsAny(), It.IsAny(),It.IsAny())扩展方法(此处:CacheExtensions.Set)不能在设置/验证前使用
System.NotSupportedException: Unsupported expression: x => x.Set(It.IsAny(), It.IsAny(), It.IsAny()) Extension methods (here: CacheExtensions.Set) may not be used in setup / verification ex
这是命名空间的缓存扩展Microsoft.Extensions.Caching.Memory
This is the Cache extension of the namespace Microsoft.Extensions.Caching.Memory
public static class CacheExtensions
{
public static TItem Set<TItem>(this IMemoryCache cache, object key, TItem value, TimeSpan absoluteExpirationRelativeToNow);
}
推荐答案
扩展方法实际上是静态方法,不能使用 moq
模拟它们.您可以模拟的是扩展方法本身使用的方法...
Extension methods are actually static methods and they cannot be mocked using moq
. What you could mock are the methods used by the extension method itself...
在您的情况下 Set
使用 CreateEntry
这是由 IMemoryCache
定义的方法,它可以被模拟.尝试这样的事情:
In your case Set
uses CreateEntry
which is the method defined by IMemoryCache
and it could be mocked. Try something like this:
memoryCacheMock
.Setup(x => x.CreateEntry(It.IsAny<object>()))
.Returns(Mock.Of<ICacheEntry>);
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