.NET 8 Moq mock GetRequiredKeyedService Setup报错

.NET 8 Moq mock GetRequiredKeyedService Setup报错

项目代码里有地方用到IServiceProvider.GetRequiredKeyedService<T>来解析服务,在写单元测试时需要Mock它,本以为像下面这样写就可以了:

var serviceProvider = new Mock<IServiceProvider>();
serviceProvider.Setup(x => x.GetRequiredKeyedService<AAA>(It.IsAny<BBB>())).Returns(new CCC());

没想到报错了:

Test method threw exception:
System.NotSupportedException: Unsupported expression: x => x.GetRequiredKeyedService(It.IsAny<Type>(), It.IsAny<object>())
Extension methods (here: ServiceProviderKeyedServiceExtensions.GetRequiredKeyedService) may not be used in setup / verification expressions.
Stack Trace: 
Guard.IsOverridable(MethodInfo method, Expression expression) line87
MethodExpectation.ctor(LambdaExpression expression, MethodInfo method, IReadOnlyList`1 arguments, Boolean exactGenericTypeArguments, Boolean skipMatcherInitialization, Boolean allowNonOverridable) line236
ExpressionExtensions.<Split>g__Split|5_0(Expression e, Expression& r, MethodExpectation& p, Boolean assignment, Boolean allowNonOverridableLastProperty) line256
ExpressionExtensions.Split(LambdaExpression expression, Boolean allowNonOverridableLastProperty) line170
Mock.SetupRecursive[TSetup](Mock mock, LambdaExpression expression, Func`4 setupLast, Boolean allowNonOverridableLastProperty) line728
Mock.Setup(Mock mock, LambdaExpression expression, Condition condition) line562
Mock`1.Setup[TResult](Expression`1 expression) line645

有点奇怪,难道GetRequiredKeyedService不是接口方法?查看.NET源代码,果然,GetRequiredKeyedService是IServiceProvider的扩展方法,而我们知道Moq是不支持Setup扩展方法的。

/// <summary>
/// Get service of type <typeparamref name="T"/> from the <see cref="IServiceProvider"/>.
/// </summary>
/// <typeparam name="T">The type of service object to get.</typeparam>
/// <param name="provider">The <see cref="IServiceProvider"/> to retrieve the service object from.</param>
/// <param name="serviceKey">An object that specifies the key of service object to get.</param>
/// <returns>A service object of type <typeparamref name="T"/>.</returns>
/// <exception cref="System.InvalidOperationException">There is no service of type <typeparamref name="T"/>.</exception>
public static T GetRequiredKeyedService<T>(this IServiceProvider provider, object? serviceKey) where T : notnull
{
ThrowHelper.ThrowIfNull(provider);
return (T)provider.GetRequiredKeyedService(typeof(T), serviceKey);
}

原因找到就好办了,翻看源码,一步步找到IServiceProvider.GetRequiredKeyedService最终调用的接口方法,然后再mock即可。

首先看下requiredServiceSupportingProvider.GetRequiredKeyedService(serviceType, serviceKey)调的是什么方法

/// <summary>
/// IKeyedServiceProvider is a service provider that can be used to retrieve services using a key in addition
/// to a type.
/// </summary>
public interface IKeyedServiceProvider : IServiceProvider
{
/// <summary>
/// Gets the service object of the specified type.
/// </summary>
/// <param name="serviceType">An object that specifies the type of service object to get.</param>
/// <param name="serviceKey">An object that specifies the key of service object to get.</param>
/// <returns> A service object of type serviceType. -or- null if there is no service object of type serviceType.</returns>
object? GetKeyedService(Type serviceType, object? serviceKey);
/// <summary>
/// Gets service of type <paramref name="serviceType"/> from the <see cref="IServiceProvider"/> implementing
/// this interface.
/// </summary>
/// <param name="serviceType">An object that specifies the type of service object to get.</param>
/// <param name="serviceKey">The <see cref="ServiceDescriptor.ServiceKey"/> of the service.</param>
/// <returns>A service object of type <paramref name="serviceType"/>.
/// Throws an exception if the <see cref="IServiceProvider"/> cannot create the object.</returns>
object GetRequiredKeyedService(Type serviceType, object? serviceKey);
}

可以看到IKeyedServiceProvider也是继承了IServiceProvider接口,这就更好办了,我们直接Mock IKeyedServiceProvider再Setup即可,将用到IServiceProvider的地方,换成IKeyedServiceProvider。

代码如下:

var serviceProvider = new Mock<IKeyedServiceProvider>();
serviceProvider.Setup(x => x.GetRequiredKeyedService(It.IsAny<AAA>(), It.IsAny<BBB>())).Returns(new CCC());

运行测试,完美。

总结

解决这个问题并不困难,但是如果.Net不开源,看不到源代码,还是有点头疼。

posted @   马行空的博客  阅读(285)  评论(0编辑  收藏  举报
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