test helper method

Given_we_are_creating_an_object_with_a_single_string_parameter.cs

using NUnit.Framework;

[TestFixture]
public class Given_we_are_creating_an_object_with_a_single_string_parameter
{
	[Test]	
	public void We_sould_test_for_null_or_whitespace_parameters()
	{
		TestHelpers.NullOrWhitespaceTest((s) => new ObjectWithStringParameter(s));
	}
}

Given_we_are_creating_an_object_with_multiple_parameters.cs

using NUnit.Framework;

[TestFixture]
public class Given_we_are_creating_an_object_with_multiple_parameters
{
	[Test]	
	public void We_sould_test_for_null_or_whitespace_parameters()
	{
		TestHelpers.NullOrWhitespaceTest((s) => new ObjectWithMultipleParameters(new MyMockObject(), s));
	}
}

TestHelpers.cs

using NUnit.Framework;
using System;

public class TestHelpers
{
	public static void NullOrWhitespaceTest(Action<string> action)
	{
		Assert.Throws<ArgumentException>(() => action(""));
		Assert.Throws<ArgumentNullException>(() => action(null));
		Assert.Throws<ArgumentException>(() => action(" "));			
	}
}