In your code you can not intercept the calls to HttpWebRequest because you create the object in the same method. If you let another object create the HttpWebRequest, you can pass in a mock object and use that to test.

So instead of this:

HttpWebRequest request = (HttpWebRequest)WebRequest.Create(_url); 

Use this:

IHttpWebRequest request = this.WebRequestFactory.Create(_url); 

In your unit test, you can pass in a WebRequestFactory which creates a mock object.

Furthermore, you can split of your stream reading code in a seperate function:

using (HttpWebResponse response = (HttpWebResponse)request.GetResponse()) { byte[] data = ReadStream(response.GetResponseStream()); return ExtractResponse(Encoding.UTF8.GetString(data)); } 

This makes it possible to test ReadStream() seperately.

To do more of an integration test, you can set up your own HTTP server which returns test data, and pass the URL of that server to your method.

In your code you can not intercept the calls to HttpWebRequest because you create the object in the same method. If you let another object create the HttpWebRequest, you can pass in a mock object and use that to test.

So instead of this:

HttpWebRequest request = (HttpWebRequest)WebRequest.Create(_url); 

Use this:

IHttpWebRequest request = this.WebRequestFactory.Create(_url); 

In your unit test, you can pass in a WebRequestFactory which creates a mock object.

Furthermore, you can split of your stream reading code in a separate function:

using (HttpWebResponse response = (HttpWebResponse)request.GetResponse()) { byte[] data = ReadStream(response.GetResponseStream()); return ExtractResponse(Encoding.UTF8.GetString(data)); } 

This makes it possible to test ReadStream() separately.

To do more of an integration test, you can set up your own HTTP server which returns test data, and pass the URL of that server to your method.