Umbraco unit test mocking

dal.cs

public class DataLayer {
  private readonly INeedAnAbstraction abs;
  
  public DataLayer() : this(new UmbracoAbstraction()) {}
  
  public DataLayer(INeedAnAbstraction abs) {
    this.abs = abs;
  }
  
  public IEnumerable<Node> FilterSomeNodes(string docTypeAlias) {
    return abs.Nodes.Where(x => x.DocumentTypeAlias == docTypeAlias);
  }
}

repository.cs

public interface INeedAnAbstraction {
  IEnumerable<Node> Nodes { get; }
}

private class UmbracoAbstraction : INeedAnAbstraction {
  public UmbracoAbstraction() {
    Nodes = nodeFactory.GetAll();
  }
  
  public IEnumerable<Node> Nodes { get; private set; }
}

tests.cs

[TestFixture]
public class Tests {
  [Test]
  public void I_Can_Haz_Tests() {
    var abs = Substitute.For<INeedAnAbstraction>();
    abs.Nodes.Returns(new[] { new Node { DocumentTypeAlias = "Foo" } });

    var dal = new DataLayer(abs);

    var result = dal.FilterSomeNodes("Foo");

    Assert.AreEqual(1, result.Count());
  }
}