Introduction

AutoFixture creates anonymous test data so you write less arrange code in unit tests.

AutoFixture helps you write unit tests with less hand-written setup. A fixture creates anonymous values during the arrange phase — strings, nested objects, and the system under test (SUT) — so you can focus on behavior instead of inventing test data.

In this tutorial

Work through these topics in order:

  1. Introduction — you are here
  2. Installation — add the NuGet package and verify restore
  3. Your first test — use Fixture.Create in a unit test
  4. Refactoring a test — shrink messy service arrange with AutoMoq and Build

Example scenario

You are testing a ShippingLabelFormatter that builds a multi-line label from a customer. The test should verify that the label includes the customer's name and city. You do not care about specific values like "Jane Doe" or "Copenhagen" — any valid customer is fine.

Example

var fixture = new Fixture();
var customer = fixture.Create<Customer>();
var sut = fixture.Create<ShippingLabelFormatter>();

var label = sut.Format(customer);

Assert.Contains(customer.Name, label);
Assert.Contains(customer.Address.City, label);

How it works

  • new Fixture() — starts the data generator for this test
  • Create<Customer>() — builds a Customer with an anonymous name and nested Address
  • Create<ShippingLabelFormatter>() — creates the SUT without a manual new
  • The asserts read from the object graph AutoFixture created, not from hard-coded strings

When constructors or dependencies change, you often change less arrange code than with hand-built objects.

Example types

The test above uses these types:

public class Address
{
    public string Street { get; set; } = string.Empty;
    public string City { get; set; } = string.Empty;
}

public sealed class Customer(string name, Address address)
{
    public string Name { get; } = name;
    public Address Address { get; } = address;
}

public sealed class ShippingLabelFormatter
{
    public string Format(Customer customer) =>
        $"{customer.Name}\n{customer.Address.Street}\n{customer.Address.City}";
}

Next steps

Installation