Xunit C# Tutorial – Complete Guide

Unleashing the power of software testing can level up your development skills like never before and today we delve into one such advantageous tool – xUnit.net, or simply xUnit, when used in C# programming. This beautiful combination can streamline the way you test your C# projects, assuring high-quality and bug-free apps or games. So, why not hop on this exciting journey and gain innovation by adding a solid layer of testing to your programming efforts?

What is xUnit for C#?

Known for being a free, open-source unit testing tool, xUnit.net is designed for .NET Framework. This toolkit comes to aid when developers need to write tests for their C# code. It is part of the versatile family of xUnit frameworks that bring a fresh approach to writing automated tests.

A Tool for The Task: Why xUnit?

The name ‘xUnit’ signifies its lineage, which traces back to a broader category of frameworks that started with the renowned tool called JUnit. But why should you include xUnit in your C# projects? Here lie your answers:

  • Firstly, xUnit is designed by the inventor of NUnit, another popular testing tool for .NET, ensuring its credibility and resourcefulness.
  • It leverages a more modern and flexible approach compared to its counterparts, encouraging developers to write robust and usable tests.
  • Adding to its components, xUnit supports .NET’s async programming model, which can be a real asset for developers in today’s evolving programming environment.
  • Finally, its clean syntax makes writing and reading tests easier, making our coding journey more straightforward and enjoyable.

Now that you’re familiar with what xUnit for C# is and why it’s a crucial tool to learn, let’s not wait anymore and start writing some code!

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Setting up xUnit in Your Project

Start by installing the xUnit testing framework in your C# project. Installing xUnit can be easily done through the NuGet Package Manager available in Visual Studio. Specify ‘xunit’ in the search bar and click on ‘Install’ to add it to your project.

// Go to Tools > NuGet Package Manager > Package Manager Console
// Type the following command in the console:
PM> Install-Package xunit

The next step is to install a test runner that visually displays our testing results. The ‘xunit.runner.visualstudio’ extension is ideal for this.

// In the Package Manager Console, type the following command:
PM> Install-Package xunit.runner.visualstudio

Writing Your First xUnit Test

Now that we’re all set, let’s proceed towards writing our first unit test using xUnit.

// Your test method
[Fact]
public void MyFirstXunitTest()
{
    // Arrange: Set input and the expected result
    int input = 10;
    int expectedResult = 20;
    
    // Act: Call the actual method 
    int actualResult = DoubleTheNumber(input);
    
    // Assert: Check if the expected result matches the actual result
    Assert.Equal(expectedResult, actualResult);
}

In this example, we marked our test method with the ‘Fact’ attribute, a distinctive feature of xUnit. The test takes an integer, doubles it, and then asserts that the result is as expected.

More Attributes: Using Theory

xUnit offers another crucial attribute – ‘Theory’, allowing us to run a single test with different input values. A single ‘Theory’ test can run multiple times with various data points, which is a big win!

[Theory]
[InlineData(10, 20)]
[InlineData(20, 40)]
public void MyTheoryTest(int input, int expectedResult)
{
    // Act
    int actualResult = DoubleTheNumber(input);
    
    // Assert
    Assert.Equal(expectedResult, actualResult);
}

Dealing with Expecting Exceptions

At times, we want our code to throw exceptions as part of its normal functioning. In such cases, we use xUnit’s ‘Assert.Throws’ method to verify these expected exceptions. Let’s take a look:

[Fact]
public void ExternalResourceUnavailableExceptionTest()
{
    // Arrange
    string invalidResourceUrl = "http://invalid.url";
    
    // Assert
    Assert.Throws<ExternalResourceUnavailableException>(() => AccessResource(invalidResourceUrl));
}

This test ensures that our method ‘AccessResource’ throws an ‘ExternalResourceUnavailableException’ when called with an invalid URL.

Organization with Collections

Organization is key! xUnit provides a means of organizing and executing test cases together through the concept of collections.

[Collection("Database collection")]
public class DatabaseTest1
{
    public DatabaseTest1()
    {
        // Constructor code here
    }

    [Fact]
    public void TestMethod1()
    {
        // Test method code here
    }
}

[Collection("Database collection")]
public class DatabaseTest2
{
    public DatabaseTest2()
    {
        // Constructor code here
    }

    [Fact]
    public void TestMethod2()
    {
        // Test method code here
    }
}

In the above code, we have two test classes that belong to the same collection. Therefore, they will be executed together.

Class and Collection Fixtures

Context sharing can be managed generously in xUnit through Class and Collection Fixtures. The class fixture supplies a constructor (for setup) and an optional Dispose method (for teardown).

public class DatabaseFixture : IDisposable
{
    public DatabaseFixture()
    {
        // Setup code here
    }

    public void Dispose()
    {
        // Cleanup (teardown) code here
    }
}

public class DatabaseTests : IClassFixture<DatabaseFixture>
{
    DatabaseFixture fixture;

    public DatabaseTests(DatabaseFixture fixture)
    {
        this.fixture = fixture;
    }

    [Fact]
    public void Test1()
    {
        // Test method code here
    }
}

Here, the DatabaseFixture Class creates a context at the beginning of each test method. The system calls Dispose after all test methods have run, providing a perfect pathway to clean up resources after testing.

Working with Mocks

For true unit tests, it’s sometimes necessary to isolate the system under test by replacing other parts of the software system with ‘mocked’ versions. Here is how we can implement mocks in xUnit using the popular Moq framework:

public interface IRepository
{
    bool Save(string data);
}

public class TestClass
{
    IRepository repo;

    public TestClass(IRepository repo)
    {
        this.repo = repo;
    }

    public bool SaveData(string data)
    {
        return repo.Save(data);
    }
}

[Fact]
public void TestMethodWithMock()
{
    var mock = new Mock<IRepository>();
    mock.Setup(repo => repo.Save(It.IsAny<string>())).Returns(true);

    TestClass cls = new TestClass(mock.Object);
    Assert.True(cls.SaveData("sample data"));
}

The Power of Assertions

Thanks to a robust assertions library, xUnit blesses us with an extensive range of assertion methods to verify test results efficiently.

[Fact]
public void AssertionTest()
{
    int expected = 5;
    int actual = Add(2, 3);
    
    // Assert with various methods
    Assert.Equal(expected, actual);
    Assert.True(actual > 1);
    Assert.False(actual < 1);
    Assert.NotNull(actual);
    Assert.InRange(actual, 1, 6);
}

This test showcases the flexibility and power of xUnit’s assertion options that can amplify our unit testing to great extent.

Testing Equality and Collection Equality

Through Equality Assertions, xUnit allows us to verify if the output of our test is equal to the expected value. Similarly, through Collection Equality Assertions, we can compare two collections for equality.

[Fact]
public void EqualityAssertionTest()
{
    // Arrange
    string expected = "Zenva";

    // Act
    string actual = GetCompanyName();

    // Assert
    Assert.Equal(expected, actual);
}

[Fact]
public void CollectionEqualityAssertionTest()
{
    // Arrange
    List<int> expectedList = new List<int>{1, 2, 3, 4, 5};

    // Act
    List<int> actualList = GetNumberList();

    // Assert
    Assert.Equal(expectedList, actualList);
}

As seen in the sample, these Equality Assertions can powerfully uplift our test coverage and integrity.

Custom Assertions

xUnit assertions aren’t sufficient for your unique scenarios? Don’t worry, xUnit provides a solution for that too! Just create your own assertion methods.

public static class CustomAsserts
{
    public static void AreEqualIgnoringCase(string expected, string actual)
    {
        if(!expected.Equals(actual, StringComparison.OrdinalIgnoreCase))
        {
            throw new Xunit.Sdk.XunitException("Strings not equal ignoring case");
        }
    }
}

[Fact]
public void CustomAssertsTest()
{
  // Arrange
  string expected = "Zenva";

  // Act
  string actual = GetCompanyName();

  // Assert using custom asserts
  CustomAsserts.AreEqualIgnoringCase(expected, actual);
}

This example introduces the concept of Custom Assertions, opening up a realm of flexible testing opportunities.

Code Coverage with Coverlet

To ensure that our codebase is well tested, it’s important to measure what proportion of our code executes during our test runs. For .NET, the industry standard solution for this is Coverlet.

// In the Package Manager Console, type the following command:
PM> Install-Package coverlet.msbuild

With this installed, we can run our test coverage with a simple command:

// This produces a result.json file with detailed coverage numbers
dotnet test /p:CollectCoverage=true

Conclusion

As we’ve explored, testing is a critical component of any software development lifecycle, and with tools like xUnit for C#, developing bug-free and maintainable applications becomes a breeze. Apart from simply learning C#, knowing how to validate your code with testing frameworks such as xUnit drastically improves your ability to deliver high-quality software.

At Zenva, we firmly believe in evolving with the tech industry’s ever-growing demands. And this doesn’t end here! There is a lot more to dig into with xUnit’s advanced functionalities. So join us, and let’s learn to code the smarter way.

Where To Go Next on Your Learning Journey?

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Conclusion

Utilizing strong testing frameworks like xUnit for C# empowers us to step up our programming game exponentially, validating our code’s integrity at each development phase. Remember, the holy grail of software development isn’t just to code, but to code flawlessly!

Mastering xUnit is indeed an invincible asset in any developer’s toolbox. However, the voyage of learning doesn’t stop here. At Zenva, we are dedicated to fueling your journey further, with our comprehensive Unity Game Development Mini-Degree, which can propel your coding and game development skills to new exciting heights. So, why wait? Join us today, to code, create, and innovate!

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