CODEWITHSUNDEEP
autofixture
Jairo Alfaro
Jairo Alfaro

Reputation: 343

how to create an object using another as a source in Autofixture?

I have something like this:

public class ModelEntity : Entity
{
    public override int Id { get; set; }

    public string FileName { get; set; }
}

public class DataTransferObject
{
    public int Id { get; set; }

    public string FileName { get; set; }
}

And I would like to do something like this:

var model = _fixture.Create<ModelEntity>(); 
var dto = _fixture.Create<DataTransferObject>().FillWith(model);

Right now I am doing the following but I am not sure if is the right way to do it

var model = _fixture.Create<ModelEntity>(); 
var dto = model.AsSource().OfLikeness<DataTransferObject>().CreateProxy();

Upvotes: 1

Views: 198

Answers (1)

Mark Seemann
Mark Seemann

Reputation: 233367

AutoFixture doesn't have a feature like that, but I think there's something better to be learned from this:

AutoFixture was originally built as a tool for Test-Driven Development (TDD), and TDD is all about feedback. In the spirit of GOOS, you should listen to your tests. If the tests are hard to write, you should consider your API design. AutoFixture tends to amplify that sort of feedback, and it may also be the case here.

It sounds like you need to be able to populate a DataTransferObject with values from a ModelEntity instance. Could this suggest that some sort of mapping would be a valuable addition to your API?

Depending on how these types are already coupled, you could consider adding a projection method to your ModelEntity class:

public class ModelEntity : Entity
{
    public override int Id { get; set; }

    public string FileName { get; set; }

    public DataTransferObject ToDataTransferObject()
    {
        return new DataTransferObject
        {
            Id = this.Id,
            FileName = this.FileName
        };
    }
}

However, the disadvantage of this approach is that it couples those two types to each other.

If you find that undesirable, you could instead introduce a dedicated Mapper Service, which can map a ModelEntity instance to a DataTransferObject object - and perhaps vice versa.

If, for some unfathomable reason, you don't want to introduce such a Mapper into your System Under Test, you can still add it as a reusable Service in your test project.

If you don't wish to write such a Mapper yourself, you could consider using something like AutoMapper for that purpose.

Upvotes: 2

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