I'm currently using NUnit 2.4.4 for these examples. See http://nunit.com/ for documentation, or to download NUnit. (The site http://nunit.org/ tends to lag behind.)

Using the 'Classic' Syntax

using System;
using System.Collections.Generic;
using System.Text;
using NUnit.Framework;

namespace NUnitDemo
{

    [TestFixture]
    public class SimpleTests
    {
        [Test]
        public void TestNada()
        {
        }

        [Test]
        public void TestMyClass()
        {
            MyClass uut = new MyClass();
            Assert.AreEqual(25, uut.Square(5));
            Assert.AreEqual(36, uut.Square(6));
        }
    }
}

Using the Constraint-based Syntax

using System;
using System.Collections.Generic;
using System.Text;
using NUnit.Framework;
using NUnit.Framework.SyntaxHelpers;

namespace NUnitDemo
{
    [TestFixture]
    public class ConstraintTests
    {
        [Test]
        public void Nada()
        {
        }

        [Test]
        public void StringsWithEqualContentsShouldBeEqual()
        {
            String aString = "a test string";
            Assert.That(aString, Is.EqualTo("a test string"));
        }

        [Test]
        public void StringsWithEqualContentsAreTheSameString()
        {
            String aString = "a test string";
            Assert.That(aString, Is.SameAs("a test string"));
        }

        [Test]
        public void MyClassCanSquareIntegers()
        {
            MyClass it = new MyClass();
            Assert.That(it.Square(5), Is.EqualTo(25));
            Assert.That(it.Square(6), Is.EqualTo(36));
        }
    }
}

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