Use ResolutionContext in tests for Automapper

Question

How do I test an Automapper ITypeConverter Converter with a ResolutionContext?

I have a complicated converter and want to test it explicitly. It needs an argument ResolutionContext which I cannot get to, nor create nor mock. Is it possible?

public class MyConverter : ITypeConverter<SourceType, TargetType>
{
    public TargetType Convert(SourceType source, TargetType destination, ResolutionContext context)
    {
       ...complicated code...
    }
}

---

Edit/Clarification: I am trying to not call myMapper.Map(... but these only the ´MyConverter.Convert` function.
I know it can be considered the wrong-way-to-test as one should only test public methods and this class/method is only public due to technical reasons and should really be private from OO point of view. But that discussion is for another forum.

Answer 1

The source code of the TypeConverter unit tests of AutoMapper itself show that they follow the regular flow:

• Set up a MapperConfiguration.
• Create a Mapper from it.
• Call one of the Map overloads.

By doing so AutoMapper takes care of passing a ResolutionContext to the Convert method.

Below code shows how the Convert method receives a ResolutionContext with a preconfigured Items dictionary.

var configuration = new MapperConfiguration(
    o => o.CreateMap<SourceType, TargetType>().ConvertUsing<MyConverter>()
    // More mappings go here.
    );

var mapper = configuration.CreateMapper();

var source = new SourceType 
{
    Name = "foo" 
};

var target = mapper.Map<TargetType>(
    source,
    o =>
    {
        o.Items["foo"] = "bar";
    });

Console.WriteLine(target.Name); // bar

public class SourceType
{
    public string Name { get; set; }
}

public class TargetType
{ 
    public string Name { get; set; }
}

public class MyConverter : ITypeConverter<SourceType, TargetType>
{
    public TargetType Convert(SourceType source, TargetType destination, ResolutionContext context)
    {
        // Complicated code goes here.
    
        return new TargetType
        {
            Name = (string)context.Items[source.Name]
        };
    }
}