Write Unit Tests (xUnit) - (ASP.NET Core Unit Testing)

Unit testing is a critical part of building reliable, maintainable software. In this page, we'll discuss how to write unit tests using xUnit in an ASP.NET Core application.

Prerequisites

Before we get started, make sure you have the following installed:

• Visual Studio or VS Code
• .NET Core SDK
• xUnit

Writing Unit Tests with xUnit

Step 1: Add xUnit to the Project

First, add the xUnit NuGet package to your project using the Package Manager Console:

Install-Package xunit

Step 2: Create a Test Project

Next, create a new project of type xUnit Test Project in your solution.

Step 3: Write Your First Test

In your new test project, add a new class for your first test and add the [Fact] attribute to your test method:

public class MyTests
{
    [Fact]
    public void Test1()
    {
        // Arrange

        // Act

        // Assert
        Assert.True(true);
    }
}

Step 4: Run the Test

Finally, build and run the test project. You should see output indicating that your test has passed.

Explanation

xUnit is a unit testing framework for .NET. It's popular because it's easy to use, extensible, and works well with .NET Core. A unit test is a piece of code that tests a small unit of functionality in your codebase, such as a single method or class.

Syntax

The syntax for writing xUnit tests is simple. You create a new class for each set of related tests, and each test method should be marked with the [Fact] attribute.

public class MyTests
{
    [Fact]
    public void Test1()
    {
        // code to test
    }
}

Example

Here's an example of a more complex test class with additional attributes:

public class MathTests
{
    [Fact]
    public void TestAddition()
    {
        // Arrange
        var math = new Math();

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

        // Assert
        Assert.Equal(4, result);
    }

    [Theory]
    [InlineData(2, 2, 4)]
    [InlineData(0, 0, 0)]
    [InlineData(100, 200, 300)]
    public void TestAdditionWithInlineData(int x, int y, int expected)
    {
        // Arrange
        var math = new Math();

        // Act
        var result = math.Add(x, y);

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

Output

When you run your tests, xUnit will output detailed information about each test, including any assertions that fail.

Test Name:	TestAddition
Test Outcome:	Passed
Duration:	3.102s

Test Name:	TestAdditionWithInlineData
Test Outcome:	Passed
Duration:	2.506s

Use

Unit testing is an essential part of modern software development, and xUnit provides an easy-to-use framework for quickly writing and running unit tests. You can use unit tests to ensure that your code is working as expected, catch regressions early, and promote more reliable code changes.

Important Points

• Unit tests should test small units of functionality in your codebase.
• xUnit is a popular unit testing framework for .NET.
• Each test method should be marked with the [Fact] attribute.

Summary

In this page, we discussed how to write unit tests with xUnit in an ASP.NET Core application. We covered the basic syntax for writing tests, showed an example of a test class with additional attributes, and explained the importance of unit testing for improving the reliability of your code.