我在 .NET Core 中有一个项目,我正在使用 AutoMapper 在我的类型之间进行映射。但我遇到了一个问题,我想模拟自定义值解析器的参数。我创建了虚拟示例来显示问题:
假设我有一个 ValueResolver,它需要访问数据库来解析给定的成员:
public class NumberProfile : Profile
{
public NumberProfile()
{
CreateMap<NumberModel, NumberDto>()
.ForMember(dest => dest.Number, opt => opt.MapFrom<NumberValueResolver>());
}
}
public class NumberValueResolver : IValueResolver<NumberModel, NumberDto, int>
{
private readonly IRepository _repository;
public NumberValueResolver(IRepository repository)
{
_repository = repository;
}
public int Resolve(NumberModel source, NumberDto destination, int destMember, ResolutionContext context)
{
return _repository.GetNumber().Number + 3;
}
}
让我们想象一下,Resolve 方法中有逻辑需要测试,我想模拟存储库以便能够测试它。 这是我在测试中尝试过的
var repositoryMock = new Mock<IRepository>();
repositoryMock.Setup(s => s.GetNumber()).Returns(new NumberModel { Number = 3 });
var mapper = new MapperConfiguration(mc =>
{
mc.AddProfile<NumberProfile>();
mc.ConstructServicesUsing(s => new NumberValueResolver(repositoryMock.Object));
});
var service = new Service(repositoryMock.Object, mapper.CreateMapper());
然后我调用服务上的一个方法来触发映射。 这个案例很好,可以工作并且测试通过。当我添加另一个 ValueResolver 时,问题就出现了。
public class NumberProfile : Profile
{
public NumberProfile()
{
CreateMap<NumberModel, NumberDto>()
.ForMember(dest => dest.Number, opt => opt.MapFrom<NumberValueResolver>())
.ForMember(dest => dest.AnotherNumber, opt => opt.MapFrom<AnotherNumberValueResolver>());
}
}
public class NumberValueResolver : IValueResolver<NumberModel, NumberDto, int>
{
private readonly IRepository _repository;
public NumberValueResolver(IRepository repository)
{
_repository = repository;
}
public int Resolve(NumberModel source, NumberDto destination, int destMember, ResolutionContext context)
{
return _repository.GetNumber().Number + 3;
}
}
public class AnotherNumberValueResolver : IValueResolver<NumberModel, NumberDto, string>
{
public int Resolve(NumberModel source, NumberDto destination, string destMember, ResolutionContext context)
{
return $"{source.Number} number(s)";
}
}
然后我想我会在测试中这样做
var repositoryMock = new Mock<IRepository>();
repositoryMock.Setup(s => s.GetNumber()).Returns(new NumberModel { Number = 3 });
var mapper = new MapperConfiguration(mc =>
{
mc.AddProfile<NumberProfile>();
mc.ConstructServicesUsing(s => new NumberValueResolver(repositoryMock.Object));
mc.ConstructServicesUsing(s => new AnotherNumberValueResolver());
});
var service = new Service(repositoryMock.Object, mapper.CreateMapper());
但是后来我得到了错误:
System.InvalidCastException:无法将“AutoMapper_app.ValueResolvers.AnotherNumberValueResolver”类型的对象强制转换为“AutoMapper_app.ValueResolvers.NumberValueResolver”类型。
我是否误解了
ConstructServicesUsing
或 ValueResolvers 的用法,还是完全不同?我错过了一些非常明显的东西吗?难道是设计不好?
有同样的问题。在研究了预期的结果之后,函数委托会根据(预期解析器的)类型返回解析器。所以类似
x.ConstructServicesUsing(t =>
{
if (t.Name.Contains("SomeObjectTypeResolver"))
return new SomeObjectTypeResolver();
// add more if statements if you have more than 2 resolvers
return new SomeOtherObjectTypeResolver();
});
这是我在单元测试中使用Moq.AutoMocker的地方。它用作 IoC 容器,您可以在容器中注册模拟,然后要求 AutoMocker 构造所需类型的对象,并且将为构造函数参数注入模拟。
然后您只需配置 AutoMapper 以使用 AutoMocker 来构建其服务,以便您的解析器使用相同的行为。这是您已经使用 ConstructServicesUsing 的地方,但不是自己创建解析器,而是使用 AutoMocker 来构造请求类型的对象。
我已经更新了上面的示例代码,以展示如何使用 AutoMocker 完成它
var repositoryMock = new Mock<IRepository>();
repositoryMock.Setup(s => s.GetNumber()).Returns(new NumberModel { Number = 3 });
var autoMocker = new AutoMock();
var mapper = new MapperConfiguration(mc =>
{
mc.AddProfile<NumberProfile>();
mc.ConstructServicesUsing(type => autoMocker.CreateInstance(type));
}).CreateMapper();
autoMocker.Use(mapper);
autoMocker.Use(repositoryMock.Object);
var service = autoMocker.CreateInstance<Service>();