Populating a Collection Property of a fixture with autofixture

Question

I have just started using AutoFixture, and i am getting the basics down (from what i can see there is much more to it) but i am having an issue and i am not 100% sure what the best practice is for stuff like this.

I am testing a controller, and part of the process is the action can return one of two views.

• If a category has children - show the category listing view
• If a category does not have children show the product listing view

So i am thinking of a few tests for that behavior, but the fixture data returned would be different. One would return a count of 0, the other a greater count then zero, so i would like the fixture to help me with that.

I have been looking around, and maybe i have to create a customisation of some sort, but was hoping the basic API could help me here. I tried this:

var category = _fixture.Build<Category>()
    .Do(x => x.SubCategories = _fixture.CreateMany<Category>(3).ToList())
    .Create();

_fakeCategoryService
    .Setup(x => x.GetById(id))
    .Returns(category);

This compiles and tests run (and fail), but the sub categories always has a count of 0, so i am thinking my call to Create Many in the do is all wrong (it kinda looks wrong but i am still unsure what it should be replaced with).

UPDATE: should read the cheat sheet a bit better!

var category = _fixture.Build<Category>()
    .With(x => x.SubCategories, _fixture.CreateMany<Category>(3).ToList())
    .Create();

This works, if there is a better way please let me know.

Answer 1

Yes, Build is correct.

---

If you want to customize the creation algorithm for a single Category use Build:

var actual = fixture
    .Build<Category>()
    .With(x => x.SubCategories, 
        fixture.CreateMany<Category>().ToList())
    .Create();

Assert.NotEmpty(actual.SubCategories);

If you want to customize the creation algorithm for all Category instances use Customize:

fixture.Customize<Category>(c => c
    .With(x => x.SubCategories,
        fixture.CreateMany<Category>().ToList()));

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

Assert.NotEmpty(actual.SubCategories);