How would I unit test a method that gets data from an RSS feed?

Question

I have a method that gets an RSS feed using LINQ to XML and returns a collection of an object that grabs only the data I need. There's really only one other method in the class I'm concerned about that you'll see in the sample -- RemoveUrlNoise.

How do I test a method like this or change it to be more testable?

    public IEnumerable<PostDetails> GetPostDetails(string rssUrl)
    {
        XElement feed = XElement.Load(rssUrl);

        var items = from item in feed.Elements("channel").Elements("item") 
                    select item;

        return items.Select(item => new PostDetails
            {
                Title = item.Element("title").Value,
                Url = RemoveUrlNoise(item.Element("guid").Value),
                PubDate = item.Element("pubDate").Value
            }).OrderBy(i => i.PubDateAsDateTime).ToList(); 
    }

Answer 1

Separate the concerns of fetching the feed XML from parsing it by extracting a class (e.g. FeedReader) to do the reading. Your IFeedReader would be generically reusable and look something like:

public interface IFeedReader
{
    XElement Load(string url);
}

with implementation

public class FeedReader : IFeedReader
{
    public XElement Load(string url)
    {
        return XElement.Load(url);
    }
}

You then inject an IFeedReader through the constructor and use it to fetch the data in your method. This lets you use a Fake or a Mock of the IFeedReader, depending on your preference, to return appropriate results for your unit test.

consider reading up on: inversion of control (IoC) and dependency injection (DI), and mock object frameworks.