C#:
Writing tests

How to:

C# developers primarily use the NUnit or xUnit frameworks for writing tests due to their flexibility and extensive feature set. Here’s a basic example using NUnit to test a simple addition function:

1. Install NUnit and NUnit3TestAdapter via NuGet Package Manager or the .NET CLI:

dotnet add package NUnit
dotnet add package NUnit3TestAdapter

2. Create a C# class library project if you haven’t done so already.

3. Write a simple function to test. For example, an addition method in a class named Calculator:

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

4. Write a test class using NUnit:

using NUnit.Framework;

namespace CalculatorTests
{
    [TestFixture]
    public class CalculatorTests
    {
        [Test]
        public void Add_AddsTwoIntegers_ReturnsCorrectSum()
        {
            // Arrange
            var calculator = new Calculator();
            int expected = 5;

            // Act
            int actual = calculator.Add(2, 3);

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

5. Run the test using your IDE’s test runner or the .NET CLI:

dotnet test

Sample Output:

Assuming your test passes, you should see output similar to this:

Test Run Successful.
Total tests: 1
     Passed: 1
 Total time: 1.2345 Seconds

Using xUnit:

If you prefer xUnit, the setup is similar to NUnit. Here’s how you’d rewrite the test example for the Calculator class using xUnit:

1. Install xUnit and xUnit.runner.visualstudio:

dotnet add package xUnit
dotnet add package xUnit.runner.visualstudio

2. Write a test class using xUnit:

using Xunit;

namespace CalculatorTests
{
    public class CalculatorTests
    {
        [Fact]
        public void Add_AddsTwoIntegers_ReturnsCorrectSum()
        {
            // Arrange
            var calculator = new Calculator();
            int expected = 5;

            // Act
            int actual = calculator.Add(2, 3);

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

3. Run the test using the .NET CLI or your IDE’s integrated test runner.

Both NUnit and xUnit provide powerful features for parameterized testing, setup/teardown operations, and organizing tests into categories, making them indispensable tools in the C# programmer’s toolkit for ensuring code quality and functionality.