如何使用 IMappingAction 通过 AfterMap 对 AutoMapper 配置文件进行单元测试

Question

我如何对使用

AfterMap

和具有注入服务的

IMappingAction

的配置文件进行单元测试。

MappingProfile.cs

public MappingProfile()
{
    CreateMap<string, string>()
        .ConvertUsing<Core.Converter.TrimStringValueConverter>();   
    CreateMap<TestModel, TestEntity>(
        .AfterMap<AfterMapAction>();
}

AfterMapAction.cs

public class AfterMapAction: IMappingAction<TestModel, TestEntity>
{
    private readonly IAfterMapService _afterMapService ;
    public AfterMapAction(IAfterMapService aftermapService)
    {
        _afterMapService  = afterMapService  ?? throw new ArgumentNullException(nameof(afterMapService));
    }

    public void Process(TestModel, TestEntity destination, ResolutionContext context)
    {
        var somevalue = _afterMapService.DoAction(source);
        ...
    }
}

测试.cs

[TestMethod]
public void AutoMapperTest()
{
    // Arrange
    var model = new TestModel { Id = "4711" , Name = "Test" };
    var mapper = new Mapper(new MapperConfiguration(cfg =>
    {
        cfg.AddProfile<MappingProfile>();
    }));

    // Act
    var mappedObject = mapper.Map<Entity>(model);

    ...
}

当我运行此测试时，出现以下异常：

System.MissingMethodException：“没有为类型‘AfterMapAction’定义无参数构造函数。

使用

cfg.ConstructServicesUsing

不起作用。它总是以 InvalidCastException 结束。

如何安排单元测试，以便AutoMapper可以实例化

AfterMapAction

？

Answer 1

我可以通过使用单元测试中的

IServiceCollection

来解决这个问题。

// Arrange
var services = new ServiceCollection();
services.AddSingleton<AfterMapAction>();
services.AddSingleton<IAfterMapService, AfterMapService>();
services.AddAutoMapper(cfg => cfg.AddProfile<MappingProfile>());

var serviceProvider = services.BuildServiceProvider();
var mapper = serviceProvider.GetService<IMapper>();

// Act

Answer 2

另一种变体是使用 CreateMapper 函数来定义自定义 IMappingAction。

// Arrange
var afterMapAction = new AfterMapAction(any_dependency_here);

var mapperConfiguration = new MapperConfiguration(cfg =>
{
    cfg.AddProfile(new MappingProfile());
});

_mapper = mapperConfiguration.CreateMapper(x =>
{
    if (x == typeof(AfterMapAction))
    {
       return afterMapAction;
    }

    return null;
});