It is critical for a software developer to assure the quality and dependability of code, and unit testing is one of the finest strategies for doing so. Developers may quickly construct extensive unit tests that confirm that each unit of software code operates as intended using xUnit, a popular unit testing tool in the.NET ecosystem. Developers can save time and resources while greatly improving overall program quality by embracing the capabilities of xUnit and introducing unit testing into the development workflow. So, let's get started on creating effective unit tests for our.NET apps right away!

Unit Testing Fundamentals
element testing is a type of software testing in which individual components or functions of a software program are tested separately to ensure that each element of the software behaves as intended. The goal is to ensure that each unit of software code operates as planned. A unit is the smallest testable component of any piece of software. A unit in object-oriented programming could be a method or a class.

The primary objectives of unit testing are as follows:

• Unit tests should be isolated, which means they should test a specific piece of functionality in the application without relying on other elements of the system.
• Unit tests should be automated and repeatable so that developers can run them regularly to catch regressions as soon as they occur.
• Unit tests should be executed quickly so that developers can receive immediate feedback on the correctness of the code.

An Overview of xUnit
xUnit is a free and open-source unit testing framework for.NET programming languages. It is a member of the xUnit testing family, which contains frameworks for other programming languages such as Java and PHP. xUnit adheres to the xUnit architecture, which is founded on four major principles:

1. Setup: Create the prerequisites for the test
2. Act: Run the unit of code that will be tested
3. Verify that the unit of code behaves as intended
4. Teardown: Remove any resources used during the test

xUnit is a simple and beautiful tool for writing unit tests for.NET applications.

Using xUnit to Implement Unit Tests in.NET
Step 1: In Visual Studio, create a new Console App.

Now create a Class name Calculator

public class Calculator
{
    public double Add(double number1, double number2)
    {
        return (number1 + number2);
    }

    public double Subtract(double number1, double number2)
    {
        return (number1 - number2);
    }
}

Now you can build this project.

Step 2. Create a new xUnit Project
We must add a reference to our original project after generating the new xUnit project. To do so, right-click on the References folder in the xUnit project and select "Add Reference." Then, choose the project you wish to refer to and press "OK." We will be able to use the classes and methods defined in our initial project in our xUnit tests as a result of this.

Now comes the drafting of the test.
Calculator cal = new Calculator();

[Fact]
public void Test_AddTwoNumber()
{
    // Arrange
    var num1 = 3.5;
    var num2 = 5.5;
    var expectedValue = 9;

    // Act
    var sum = cal.Add(num1, num2);

    //Assert
    Assert.Equal(expectedValue, sum, 1);
}

[Fact]
public void Test_SubtractTwoNumber()
{
    // Arrange
    var num1 = 6;
    var num2 = 2;
    var expectedValue = 4;

    // Act
    var sum = cal.Subtract(num1, num2);

    //Assert
    Assert.Equal(expectedValue, sum, 1);
}

Step 3: Carry out the test
To run the test, right-click on the xUnit Test project and choose "Run Test". This will run all of the unit tests in the project and display the results. Make sure to perform this after you've written the unit tests to ensure they're operating properly and catching any regressions as soon as they appear.

The results of the test are presented on the screen once you run it. This is an important phase in the unit testing process since it aids in the identification of any flaws or bugs in the code. Developers may discover any regressions as soon as they appear by running the test regularly, allowing them to fix the problems quickly and efficiently. Unit tests should also be automated and repeatable, which means they can be run fast and easily, providing developers with immediate feedback on the quality of the code. With xUnit, developers can simply create extensive unit tests for their.NET projects, assuring the codebase's reliability and maintainability.