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Ana Rența
Ana Rența

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Unit Testing in .NET: Getting Started with xUnit and NUnit

Think of unit tests as rehearsals before a big performance. They let you test your steps, refine your moves, and ensure everything works flawlessly when it’s showtime. Unit tests ensure that individual parts of your code work as expected, making the application robust and reliable. While it might feel tedious at first, the long-term benefits—like confidence in your codebase, easier debugging, and safer refactoring—make it an essential practice in software development.

xUnit vs. NUnit

Both frameworks are great for .NET testing, but they have unique strengths:

  • xUnit: lightweight and modern, with features like parallel test execution and concise syntax ([Fact], [Theory]).
  • NUnit: mature framework with extensive features, including [Test] and [TestCase] attributes for flexibility.

Here’s how to get started with each:

Writing a Test with xUnit

public class Calculator
{
    public int Add(int a, int b) => a + b;
}

using Xunit;

public class CalculatorTests
{
    [Fact]
    public void When_AddingTwoNumbers_Then_ReturnsCorrectSum()
    {
        // Arrange
        var calculator = new Calculator();

        // Act
        var result = calculator.Add(2, 3);

        // Assert
        Assert.Equal(5, result);
    }
}
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Writing a Test with NUnit

public class Calculator
{
    public int Add(int a, int b) => a + b;
}

using NUnit.Framework;

[TestFixture]
public class CalculatorTests
{
    [Test]
    public void When_AddingTwoNumbers_Then_ReturnsCorrectSum()
    {
        // Arrange
        var calculator = new Calculator();

        // Act
        var result = calculator.Add(2, 3);

        // Assert
        Assert.AreEqual(5, result);
    }
}
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Best Practices

  • Keep Tests Simple: test one thing at a time.
  • Use Clear Names: descriptive names like When_AddingTwoNumbers_Then_ReturnsCorrectSum help readability.
  • Follow AAA Patter, structure tests as:
    • Arrange: Set up test data.
    • Act: Perform the action being tested.
    • Assert: Verify the result.
  • Mock Dependencies: use mocking libraries like Moq to isolate units.
  • Test Edge Cases: don’t just test the happy path; include boundary and error scenarios.

Unit testing in .NET with xUnit or NUnit may seem challenging initially, but it’s a crucial step toward creating reliable, maintainable software. It’s your safety net, helping you catch problems early and adapt your code as it evolves. Start small, be consistent, and see how your codebase transforms into a strong platform for growth.

What are your favorite tips or experiences with unit testing? I’d love to hear them-share in the comments below!

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Billboard image

The Next Generation Developer Platform

Coherence is the first Platform-as-a-Service you can control. Unlike "black-box" platforms that are opinionated about the infra you can deploy, Coherence is powered by CNC, the open-source IaC framework, which offers limitless customization.

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