(I originally planned this to be a single article, but because of the scope decided to split it into two parts. This first part explores the basics of using Sun’s
HttpServer to conduct functional HTTP testing. Part 2 revisits the following test using JUnit 4.7’s new interceptors (rules) feature and demonstrates a simpler HTTP handler.)
At work, we recently had the need to perform functional testing of a custom client that used HTTP as a transport. This isn’t strictly unit testing since we’re conducting actual HTTP over a socket & port instead of stubbing out or mocking the server, but in this case that was the only real way to test the client.
I could’ve fired up a standalone Web server and used that, but decided against it for a couple of reasons.
First, I wanted to have the server respond in a specific way to a particular client request. For example, if the request was for
GET /1234.xml I might want to respond with an
HTTP 200 and an XML response body. Another request for
GET /0.xml might return an
HTTP 404 instead.
To do that using, say, a Servlet container would mean writing multiple Servlets (mapped to various request URI) or a ‘rich’ Servlet with additional complexity. I didn’t want to have to write tests to test my test scaffolding!
Secondly, a standalone server would have to be started and stopped outside of our standard compile/test/package process (using Maven). Other people wouldn’t be able to run the tests successfully without having the test server up as well.
Clearly, the best way to go was to use an embedded HTTP server, which would allow us to provide specific responses tailored for each unit test.
As luck would have it, it turns out that Sun’s Java 6 implementation comes with a lightweight HTTP server API built in. Read on as I demonstrate the basic use of Sun’s HTTP server classes to write a functional test.