Here's one way to do it.
Start by implementing a SpecimenBuilder that tells AutoFixture to skip assigning a value for collection property:
public class CollectionPropertyOmitter : ISpecimenBuilder
{
public object Create(object request, ISpecimenContext context)
{
var pi = request as PropertyInfo;
if (pi != null
&& pi.PropertyType.IsGenericType
&& pi.PropertyType.GetGenericTypeDefinition() == typeof(ICollection<>))
return new OmitSpecimen();
return new NoSpecimen(request);
}
}
Then encapsulate that in a Customization:
public class DoNotFillCollectionProperties : ICustomization
{
public void Customize(IFixture fixture)
{
fixture.Customizations.Add(new CollectionPropertyOmitter());
}
}
The following tests now pass:
[Fact]
public void CreatePersonWithoutFillingCollectionProperty()
{
var fixture = new Fixture().Customize(new DoNotFillCollectionProperties());
var actual = fixture.Create<Person>();
Assert.Null(actual.OtherClasses);
}
[Fact]
public void CreateManyStillWorks()
{
var fixture = new Fixture().Customize(new DoNotFillCollectionProperties());
var actual = fixture.CreateMany<Person>();
Assert.NotEmpty(actual);
}
[Fact]
public void CreatListStillWorks()
{
var fixture = new Fixture().Customize(new DoNotFillCollectionProperties());
var actual = fixture.Create<List<Person>>();
Assert.NotEmpty(actual);
}
[Fact]
public void CreateCollectionStillWorks()
{
var fixture = new Fixture().Customize(new DoNotFillCollectionProperties());
var actual = fixture.Create<ICollection<Person>>();
Assert.NotEmpty(actual);
}