How should I unit test threaded code?

Question

I have thus far avoided the nightmare that is testing multi-threaded code since it just seems like too much of a minefield. I\'d like to ask how people have gone about test

Answer 1

For J2E code, I've used SilkPerformer, LoadRunner and JMeter for concurrency testing of threads. They all do the same thing. Basically, they give you a relatively simple interface for administrating their version of the proxy server, required, in order to analyze the TCP/IP data stream, and simulate multiple users making simultaneous requests to your app server. The proxy server can give you the ability to do things like analyze the requests made, by presenting the whole page and URL sent to the server, as well as the response from the server, after processing the request.

You can find some bugs in insecure http mode, where you can at least analyze the form data that is being sent, and systematically alter that for each user. But the true tests are when you run in https (Secured Socket Layers). Then, you also have to contend with systematically altering the session and cookie data, which can be a little more convoluted.

The best bug I ever found, while testing concurrency, was when I discovered that the developer had relied upon Java garbage collection to close the connection request that was established at login, to the LDAP server, when logging in. This resulted in users being exposed to other users' sessions and very confusing results, when trying to analyze what happened when the server was brought to it's knees, barely able to complete one transaction, every few seconds.

In the end, you or someone will probably have to buckle down and analyze the code for blunders like the one I just mentioned. And an open discussion across departments, like the one that occurred, when we unfolded the problem described above, are most useful. But these tools are the best solution to testing multi-threaded code. JMeter is open source. SilkPerformer and LoadRunner are proprietary. If you really want to know whether your app is thread safe, that's how the big boys do it. I've done this for very large companies professionally, so I'm not guessing. I'm speaking from personal experience.

A word of caution: it does take some time to understand these tools. It will not be a matter of simply installing the software and firing up the GUI, unless you've already had some exposure to multi-threaded programming. I've tried to identify the 3 critical categories of areas to understand (forms, session and cookie data), with the hope that at least starting with understanding these topics will help you focus on quick results, as opposed to having to read through the entire documentation.