TDD with .NET - null coalescing for defaults

Yet another post in the TDD with .NET series... 

There are some fun tricks that can make code a little bit more elegant for advanced coders, though newer developers will take some adjusting.

Suppose there is a business rule that when a name isn't valid (as defined by is_valid), we should display 'unknown.'

I've created a Name class, which stores a FirstName, MiddleInitial and LastName. I have a property named FullName that returns a string.

namespace EduTest

{

    [TestFixture]

    public class NameTests

    {

        [Test]

        public void FullName_is_null_if_incomplete()

        {

            Name mick = Factory.Name;

            mick.FirstName = null;

            Assert.Equals(null, mick.FullName);

        }

    }

}

seven tests, one failure

public string FullName

{

    get

    {

        if (this.is_valid)

        {

            StringBuilder full_name = new StringBuilder();

            full_name.Append(FirstName);

            if (MiddleInitial.HasValue)

            {

                full_name.Append(' ');

                full_name.Append(MiddleInitial);

                full_name.Append('.');

            }

            full_name.Append(' ');

            full_name.Append(LastName);

            return full_name.ToString();

        }

        else

        {

            return null;

        }

    }

}

seven tests, zero failures

This method is long-ish. I would like to refactor it, but I'll hold off for now. I'm also wondering whether this logic actually belongs in this method... but without any feedback from another developer or a good idea to persue, I'm going to leave it alone until it becomes painful or I think of a better option.

Next test...

namespace EduTest

{

    [TestFixture]

    public class NameTests

    {

        [Test]

        public void ToString_is_Unknown_when_name_is_incomplete()

        {

            Name prince = new Name();

            prince.FirstName = "Prince";

            prince.LastName = null;

            Assert.Equals("Unknown", prince.ToString());

        }

    }

}

eight tests, one failure

Now I'm going to use the cool null-coalescing operator ( ?? ).

namespace Edu

{

    public class Name

    {

        public override string ToString()

        {

            return FullName ?? "Unknown";

        }

    }

}

The null coalescing operator allows you to specify what value you want used if the first value is null.

"hello" ?? "value" results in "hello"

null ?? "default" results in "default"

eight tests, zero failures