Writing your first test

Quick Start: Complete Example

Here's a complete TUnit test class with all necessary using statements:

using TUnit.Assertions;
using TUnit.Assertions.Extensions;
using TUnit.Core;

namespace MyTestProject;

public class CalculatorTests
{
    [Test]
    public async Task Add_WithTwoNumbers_ReturnsSum()
    {
        // Arrange
        var calculator = new Calculator();

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

        // Assert
        await Assert.That(result).IsEqualTo(5);
    }
}

Important: TUnit does not require a [TestClass] attribute. Unlike MSTest or NUnit, you only need the [Test] attribute on your test methods.

Step-by-Step Guide

Auto-Imported Namespaces

The TUnit package automatically configures global usings for TUnit.Core, TUnit.Assertions, and TUnit.Assertions.Extensions. The explicit using statements in the examples below are shown for clarity — you don't need them in practice.

Start by creating a new class:

namespace MyTestProject;

public class MyTestClass
{

}

Now add a method with a [Test] attribute on it:

using TUnit.Core;

namespace MyTestProject;

public class MyTestClass
{
    [Test]
    public async Task MyTest()
    {

    }
}

That's it. That is your runnable test.

We haven't actually made it do anything yet, but we should be able to build our project and run that test.

Tests will pass if they execute successfully without any exceptions.

Test Method Signatures

Test methods can be either synchronous or asynchronous:

[Test]
public void SynchronousTest()  // ✅ Valid - synchronous test
{
    var result = Calculate(2, 3);
    // Simple synchronous test without assertions
}

[Test]
public async Task AsyncTestWithAssertions()  // ✅ Recommended - asynchronous test
{
    var result = Calculate(2, 3);
    await Assert.That(result).IsEqualTo(5);  // Assertions must be awaited
}

Important Notes:

• If you use Assert.That(...), your test must be async Task — assertions return awaitable objects that won't execute without await
• Synchronous void tests are allowed but cannot use assertions
• async void tests are not allowed and will cause a compiler error

See Awaiting Assertions for more details.

Let's add some code to show you how a test might look once finished:

using TUnit.Assertions;
using TUnit.Assertions.Extensions;
using TUnit.Core;

namespace MyTestProject;

public class MyTestClass
{
    [Test]
    public async Task MyTest()
    {
        var result = Add(1, 2);

        await Assert.That(result).IsEqualTo(3);
    }

    private int Add(int x, int y)
    {
        return x + y;
    }
}

Here you can see we've executed some code and added an assertion. We'll go more into that later.

Common Test Patterns

Testing Boolean Returns

When testing methods that return boolean values, use IsTrue() or IsFalse():

using TUnit.Assertions;
using TUnit.Assertions.Extensions;
using TUnit.Core;

namespace MyTestProject;

public class ValidatorTests
{
    [Test]
    public async Task IsPositive_WithNegativeNumber_ReturnsFalse()
    {
        // Arrange & Act
        var result = Validator.IsPositive(-1);

        // Assert
        await Assert.That(result).IsFalse();
    }

    [Test]
    public async Task IsPositive_WithPositiveNumber_ReturnsTrue()
    {
        // Arrange & Act
        var result = Validator.IsPositive(5);

        // Assert
        await Assert.That(result).IsTrue();
    }
}

public static class Validator
{
    public static bool IsPositive(int number)
    {
        return number > 0;
    }
}

Testing with Multiple Assertions

using TUnit.Assertions;
using TUnit.Assertions.Extensions;
using TUnit.Core;

namespace MyTestProject;

public class StringTests
{
    [Test]
    public async Task ProcessString_WithValidInput_ReturnsExpectedResult()
    {
        // Arrange
        var input = "hello";

        // Act
        var result = input.ToUpper();

        // Assert
        await Assert.That(result).IsEqualTo("HELLO");
        await Assert.That(result).Length().IsEqualTo(5);
        await Assert.That(result.StartsWith("HE")).IsTrue();
    }
}

Next: Run Your Tests →