存根或模拟 IMapper 返回派生的类，其中 Base Expected

Question

我有一个 class 在构造函数中接受一个 IMapper 像这样

public Foo(IMapper mapper)

在 Foo 的代码中有这一行

var dao = _mapper.Map<BaseDAO>(obj);

BaseDAO 有 3 个子类型，在我这样设置的真实代码中

CreateMap<Base, BaseDAO>()
     .Include<Child1, Child1DAO>()
     .Include<Child2, Child2DAO>()
     .Include<Child3, Child3DAO>();

我想模拟上面那行

var dao = _mapper.Map<BaseDAO>(obj);

因此，如果传入 Child1，则将返回 Child1DAO，其他子类型也是如此。我试图存根 IMapper 但下面的方法 returns 一个错误说

Child1DAO cannot be implicitly converted to a TDestination

我试着模仿 IMapper 但也无法让它工作。

public TDestination Map<TDestination>(object source)
{
    return new Child1DAO();
}

有什么想法吗？

Answer 1

为了这个例子的目的，假设下面的class是被测对象

public class Foo {
    private IMapper mapper;
    public Foo(IMapper mapper) {
        this.mapper = mapper;
    }

    public BaseDAO Bar(object obj) {
        var dao = mapper.Map<BaseDAO>(obj);
        return dao;
    }
}

其中 IMapper 依赖项定义了以下契约

public interface IMapper {
    /// <summary>
    /// Execute a mapping from the source object to a new destination object.
    /// The source type is inferred from the source object.
    /// </summary>
    /// <typeparam name="TDestination">Destination type to create</typeparam>
    /// <param name="source">Source object to map from</param>
    /// <returns>Mapped destination object</returns>
    TDestination Map<TDestination>(object source);

    //...
}

以下测试演示，使用最小起订量，

Mock IMapper Returning Derived Classes where Base Expected

[TestClass]
public class TestClass {
    [TestMethod]
    public void _TestMethod() {
        //Arrange
        var mock = new Mock<IMapper>();
        var foo = new Foo(mock.Object);

        mock
            //setup the mocked function
            .Setup(_ => _.Map<BaseDAO>(It.IsAny<object>()))
            //fake/stub what mocked function should return given provided arg
            .Returns((object arg) => {
                if (arg != null && arg is Child1)
                    return new Child1DAO();
                if (arg != null && arg is Child2)
                    return new Child2DAO();
                if (arg != null && arg is Child3)
                    return new Child3DAO();

                return null;
            });

        var child1 = new Child1();

        //Act
        var actual = foo.Bar(child1);

        //Assert
        Assert.IsNotNull(actual);
        Assert.IsInstanceOfType(actual, typeof(BaseDAO));
        Assert.IsInstanceOfType(actual, typeof(Child1DAO));
    }
}

存根或模拟 IMapper 返回派生的类，其中 Base Expected

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存根或模拟 IMapper 返回派生的 类，其中 Base Expected

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存根或模拟 IMapper 返回派生的类，其中 Base Expected