Overview

FakeUp is small project that allows to generate fake data objects with complex structure for tests. The goal is to create API that is concise and modular, so creating fixtures for nested and/or dependent structures is painless or at least a lot less painful. It is just worse version of AutoFixture but some tasks that I was needed can be done more easily with FakeUp since it have to narrower scope and more specialized features.

Features highlight

• Filling values based on relative paths
• Sharing state

Filling values based on relative paths

For use when you have reoccurring structures with some special cases.

class Foo {
   Bar Bar { get; }    
   Baz Baz { get; }
   string Value { get; }
}
class Bar {
   Baz Baz { get; }
}
class Baz {
   string Value { get; }
}

When creating fixture with following code

var result = FakeUp.NewObject<Foo>(o => o
   .FillAll<string>().With("default")
   .Fill((Bar bar) => bar.Baz.Value).With("bar baz")
)

You will receive the following:

Foo
   Bar.Baz.Value: "bar baz"
   Baz.Value: "default"
   Value: "default"

Sharing state

When you have values that are dependent on one another, you can use State to manage shared values. For example we have following structure:

class ReceiptBook {
    public List<Ingredient> Ingredients { get; set; }
    public List<FoodReceipt> Receipts { get; set; }
}
class FoodReceipt {
    public string Name { get; set; }
    public List<Ingredient> Ingredients { get; set; }
}
class Ingredient {
    public string Name { get; set; }
}

We want ReceiptBook.Ingredients to contain all ingredients used in all FoodReceipts. We can achieve this using object that will track all added ingredients:

class FoodReceiptState
{    
    public List<Ingredient> AllIngredients { get; } = new List<Ingredient>();

    public Ingredient GetIngredient()
    {
        if (!this.AllIngredients.Any() || new Random().NextDouble() > 0.5)
        {
            var ingredient = NewIngredient();
            this.AllIngredients.Add(ingredient);
            return ingredient;
        }

        return this.AllIngredients[this.Random.Next(0, this.AllIngredients.Count)];
    }

    private Ingredient NewIngredient() => FakeUp.NewObject<Ingredient>(o => o.FillAll<string>().WithGuid());
}

The idea is, that every time FakeUp will require FoodReceipt.Ingredient we will return either new Ingredient and add it to list or return excising one. So AllIngredients will always contain all generated ingredients.

Now following declaration will create object with required structure:

FakeUp.NewObject<ReceiptBook>(o => o
    .WithCollectionsSize(3)
    .AddState(() => new FoodReceiptState())
    
    .FillAll<string>().WithGuid()

    .FillAll<Ingredient>()
    .With(ctx => ctx.GetState<FoodReceiptState>().GetIngredient())

    .Fill(book => book.Ingredients)
    .With(ctx => ctx.GetState<FoodReceiptState>().AllIngredients)
);