Unit testing is a vital practice in C# software development, ensuring code reliability and quality. However, the process of setting up tests with realistic data can be time-consuming and repetitive. This is where AutoFixture comes in – a powerful library that simplifies the creation of unit tests in C#.


In this article, we explore how the library streamlines test setups and enhances the efficiency of unit testing, supported by insightful code samples.


In traditional unit testing, developers spend significant time manually creating objects and setting up test scenarios. AutoFixture facilitates this process by automating the generation of test data, resulting in accelerated test setups.


Let's discover how to accomplish this with the help of C# code samples.

  1. Install AutoFixture via NuGet package manager

  2. Create an instance of Fixture:
    var fixture = new Fixture();

  3. Generate test data using AutoFixture:
    //Automatically populates properties
    var customer = fixture.Create<Customer>();

  4. Use the generated test data in a test scenario:
    var result = customer.PlaceOrder();

  5. Assert the outcome of the test:

Enhanced test data generation

AutoFixture goes beyond mere object creation and offers customisable data generation strategies. Developers can effortlessly generate diverse and realistic test data to cover a wide range of scenarios.


Let's take a look at how AutoFixture helps in this regard.

  • Customise data generation for specific properties:
    fixture.Customize<Customer>(c => c
    .Without(x => x.LastOrderDate)//Exclude specific property 
    .With(x => x.IsPreferredCustomer, true));//Set a specific value

  • Generate test data with customisations:
    var customer = fixture.Create<Customer>();
  • Assert that the customised data matches expectations:


Maintainable and resilient tests

As the System Under Test (SUT) evolves, maintaining existing tests can become challenging. AutoFixture simplifies this process by adapting to changes in the SUT automatically. This adaptability reduces the need for frequent modifications to the test code. Let's see an example.


  • Assume a change in the Customer class:
    public class Customer 
    public string Name { get; set; } 
    public short Age { get; set; }  // Type changed from int32 

  • No changes required in the test code:
    var customer = fixture.Create<Customer>();

  • Assert the unchanged test scenario:



AutoFixture is a game-changer for C# developers seeking to optimise unit testing practices. By automating the generation of test data and accelerating test setups, it allows developers to focus on writing effective test scenarios.


With customisable data generation, maintainable tests, and seamless integration with the C# ecosystem, it empowers developers to build resilient and efficient unit tests.


Therefore, incorporating AutoFixture into your C# unit testing toolkit is a step towards enhancing productivity and code quality in your software development projects.

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