CODEWITHSUNDEEP
c#autofixture
Andrew Corcoran
Andrew Corcoran

Reputation: 31

How can I populate an instance of an object with random values?

Is there any way I can give AutoFixture an instance of an object and have it go through all the setters and set random data? The wiki examples only show how to obtain an instance from AutoFixture, e.g.

var autoGeneratedClass = fixture.Create<ComplexParent>();

My example use case is a factory method which generate instances of objects with dynamic properties based on a configuration. I want to test that my methods correctly, detect and interact (e.g. copy) these dynamic properties.

dynamic dynamicPropertyObject1 = factoryMethod(configuration);
dynamic dynamicPropertyObject2 = factoryMethod(configuration);
dynamicPropertyObject1.propA = random.Next();
dynamicPropertyObject1.CopyTo(dynamicPropertyObject2); 
Assert.That(dynamicPropertyObject2.propA, Is.EqualTo(dynamicPropertyObject1.propA);

Thanks

Upvotes: 3

Views: 1405

Answers (1)

Mark Seemann
Mark Seemann

Reputation: 233367

AutoFixture has a lot of built-in heuristics for creating objects, including some for factory methods.

If AutoFixture finds no public constructors on a type, it starts to look for factory methods; i.e. static methods that return objects of the type of the class that defines that static method, e.g.

public class Foo
{
    public static Foo CreateFoo();

    // ... other members
}

If, on the other hand, a factory method exists on another class, you'll need to help AutoFixture a bit. The easiest way would be to use the Customize method:

fixture.Customize<Foo>(c => c
    .FromFactory(() => FooFactory.CreateFoo())
    .WithAutoProperties());

When you subsequently ask a Fixture object for a Foo object, FooFactory.CreateFoo() will be invoked, and because of WithAutoProperties that object will be populated with data created by AutoFixture.

Upvotes: 2

Related Questions