Question

I am testing a static method that builds a URL string after checking proxies and hostnames and all kinds of things. This method internally relies on the static flag System.Net.Sockets.Socket.OSSupportsIPv6. Because it’s static, I cannot mock this dependency.

EDIT: (This is simplified down a lot… I can’t modify the structure of the method with the flag to accept a true/false).

On XP development machines, the method under question returns a predictable string result (in this case, http://hostname/…. ). Our build server, which support IPv6, returns a totally different result (it gives me something like http://192.168.0.1:80/….). Please don’t ask why – the point is that there are two different output types that vary on an operating system dependency.

The test needs to validate that the returned hostname or IP address is valid. The outputs are easy to check. The problem is that I can only get one of the possible outputs, depending on which machine the test is run on.

What’s the best practice for writing the test in this case? Do I put an if statement in my test which checks the flag and then looks for the two different outputs? This seems sketchy to me because

1. the test is behaving differently
   depending on the environment it’s
   run in

2. I’m basically coupling the test
   to the method, because you need to
   know the internals of the method to
   set up the two cases.

Do I set up two tests, one for each environment, that simply pass if they’re in the wrong environment? Do I write some complex regular expression that can separate out what kind of result it got and use more if/else logic to verify it?

Any suggestions would help!

Answer 1

Can you hide the static method behind an abstract interface?

interface ISupportIPv6
{
  bool supported { get; }
}

//class for unit testing
class TestSupportsIPv6 : ISupportIPv6
{
  public bool supported { get { return true; } }
}

//another class for more unit testing
class TestDoesNotSupportIPv6 : ISupportIPv6
{
  public bool supported { get { return false; } }
}

//class for real life (not unit testing)
class OsSupportsIPv6 : ISupportIPv6
{
  public bool supported { get {
    return System.Net.Sockets.Socket.OSSupportsIPv6; } }
}