Create testdata with List<string>, Autofixture

Question

Trying to get this simple test to work:

public class MyClass
{
    public string Text { get; set; }
    public List<string> Comments { get; set; }

}
[TestClass]
public class UnitTest1
{
    [TestMethod]
    public void TestMethod1()
    {
        var fixture = new Fixture();
        fixture.Customize<string>(c => c.FromSeed(s => s)); //Just return propertyname, no GUID appended
        var test = fixture.Create<MyClass>();

    }
}

but I keep getting the error

The decorated ISpecimenBuilder could not create a specimen based on the request: System.String. This can happen if the request represents an interface or abstract class; if this is the case, register an ISpecimenBuilder that can create specimens based on the request. If this happens in a strongly typed Build<T> expression, try supplying a factory using one of the IFactoryComposer<T> methods.`

If I remove the Customize line, is seems to work...

Not quite sure what I need to do to make it work

Nikos Baxevanis · Accepted Answer · 2014-07-04 14:13:12Z

2

You can create string instances without appending a GUID by customizing the Fixture instance as shown below:

public void GuidsAreNotAppendedOnStringValues()
{
    var fixture = new Fixture();
    var expected = string.Empty;
    fixture.Customizations.Add(
        new StringGenerator(() => expected));

    var actual = fixture.Create<MyClass>();

    Assert.Equal(expected, actual.Comments.Aggregate((x, y) => x + y));
}

That way also the Text property is Text, instead of Texte85e2f6f-c1a3-47c7-baf2-4756c498f523.

answered Jul 4, 2014 at 14:13

Nikos Baxevanis

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1 Comment

Søren M. Olesen Over a year ago

But then it seems like all the entries in my comment list are empty... would like them to be filled with something too...

Søren M. Olesen · Accepted Answer · 2014-07-07 07:04:24Z

Ended up, adding my own ISpecimenBuilder

public class TextBuilder : ISpecimenBuilder
{
    public object Create(object request, ISpecimenContext context)
    {
        var pi = request as PropertyInfo;
        if (pi == null)
            return new NoSpecimen(request);
        if (pi.PropertyType == typeof(string))
            return pi.Name;
        if (pi.PropertyType == typeof(IList<string>) || pi.PropertyType == typeof(List<string>))
        {
            var tmps = (List<string>)context.Resolve(typeof(List<string>));
            for (var n = 0; n != tmps.Count; ++n)
                tmps[n] = pi.Name + n.ToString(CultureInfo.InvariantCulture);
            return tmps;
        }
        return new NoSpecimen(request);
    }
}

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