How to write unit test code more simply.

UnitTest1.cs

// PM> Install-Package ChainingAssertion
// http://nuget.org/packages/ChainingAssertion
// http://chainingassertion.codeplex.com/

using System;
using Microsoft.VisualStudio.TestTools.UnitTesting;

public class DateHelper
{
    public static DateTime? ToNullableDate(string input)
    {
        if (string.IsNullOrWhiteSpace(input)) return null;
        DateTime d;
        if (DateTime.TryParse(input, out d)) return d;
        throw new ArgumentException();
    }
}

[TestClass]
public class UnitTest1
{
    [TestMethod]
    public void TestMethod1()
    {
        DateHelper.ToNullableDate("2012/03/01").Is(new DateTime(2012, 3, 1));
        DateHelper.ToNullableDate("").IsNull();
        AssertEx.Throws<ArgumentException>(() => DateHelper.ToNullableDate("invalidValue"));
    }
}