NUnit

// Equality asserts
Assert.AreEqual(object expected, object actual);
Assert.AreEqual(object expected, object actual, string message, params object[] parms);

Assert.AreNotEqual(object expected, object actual);
Assert.AreNotEqual(object expected, object actual, string message, params object[] parms);

// Identity asserts
Assert.AreSame(object expected, object actual);
Assert.AreSame(object expected, object actual, string message, params object[] parms);

Assert.AreNotSame(object expected, object actual);
Assert.AreNotSame(object expected, object actual, string message, params object[] parms);

// Condition asserts
// (For simplicity, methods with message signatures are omitted.)
Assert.IsTrue(bool condition);
Assert.IsFalse(bool condition);

Assert.IsNull(object anObject);
Assert.IsNotNull(object anObject);

Assert.IsNaN(double aDouble);

Assert.IsEmpty(string aString);
Assert.IsNotEmpty(string aString);

Assert.IsEmpty(ICollection collection);
Assert.IsNotEmpty(ICollection collection);

using NUnit.Framework;
 
[TestFixture]
public class ExampleTestOfNUnit
{
    [Test]
    public void TestMultiplication()
    {
        Assert.AreEqual(4, 2*2, "Multiplication");
        
        // Equivalently, since version 2.4 NUnit offers a new and
        // more intuitive assertion syntax based on constraint objects
        // [http://www.nunit.org/index.php?p=constraintModel&r=2.4.7]:
        Assert.That(2*2, Is.EqualTo(4), "Multiplication constraint-based");
    }
}

// The following example shows different ways of writing the same exception test.

[TestFixture]
public class AssertThrowsTests
{
    [Test]
    public void Tests()
    {
        // .NET 1.x
        Assert.Throws(typeof(ArgumentException),
            new TestDelegate(MethodThatThrows));
	    
        // .NET 2.0
        Assert.Throws<ArgumentException>(MethodThatThrows);
        Assert.Throws<ArgumentException>(
	    delegate { throw new ArgumentException(); });

        // Using C# 3.0	    
        Assert.Throws<ArgumentException>(
            () => { throw new ArgumentException(); });
    }
    
    void MethodThatThrows()
    {
        throw new ArgumentException();
    }
}

// This example shows use of the return value to perform additional verification of the exception.

[TestFixture]
public class UsingReturnValue
{
    [Test]
    public void TestException()
    {
        MyException ex = Assert.Throws<MyException>(
            delegate { throw new MyException("message", 42); });
        Assert.That(ex.Message, Is.EqualTo("message"));
        Assert.That(ex.MyParam, Is.EqualTo(42)); 
    }
}

// This example does the same thing using the overload that includes a constraint.

[TestFixture]
public class UsingConstraint
{
    [Test]
    public void TestException()
    {
        Assert.Throws(Is.Typeof<MyException>()
                                 .And.Message.EqualTo("message")
                                 .And.Property("MyParam").EqualTo(42),
            delegate { throw new MyException("message", 42); });
    }
}