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Tuesday, February 9, 2010

Do hackers make good testers?

Someone on LinkedIn was asking about becoming an ethical hacker.

Back before I got into computers I understood the term hacker to mean someone who learns from trial and error. So a computer hacker was someone who tried things and remembered the results. Now if you started hacking a computer site you probably found things the average user didn't and potentially crashed the site. Because a lot of what was happening on the server was hidden from you, you had no idea what trying different things would do until you tried them. And even then you might not know what actually happened other than you lost the connection.

If I was hacking a web site or piece of software I would need to narrow things down. If I tried something I might know it will be one of four things that caused the resulting crash. If I tried something else, it might have three things in common with the first hack. If it crashed you might say that one thing that is not common to both hacks is not the crash. You'd be wrong. You're assuming there is one crash. Could be there are two different crashes. :)

Keeping your mind open like that is what is needed to be a good hacker. I picture things in terms of Venn diagrams. Overlapping areas are not important as it could be one or the other. The things which can only happen in one area are the interesting bits.

There is something about this way of thinking that makes it easy to find defects. It is almost like detective work. You have some evidence and you need to see if you can find more. You poke and probe to see what falls out. You interrogation the application under test and see what secrets it reveals. You keep track of cause and effect. I do this over a long period of time. You look for patterns.

Case in point, I was testing an application that had a load feature. There was a defect in the load routine. I filed the defect and the developer fixed it. Once I could load, I could save. A similar defect existed in the save routine. Programmers make common mistakes. Is there more than one place that programmer could make the same mistake? I always take the time to find out what the defect was (from a technical standpoint) and what was really happening.

After a while I can almost predict what errors will occur in a program.

The other trait I have and see in other good testers is curiosity. I'm always wondering why things work the way they do. Before computers I'd take apart lawnmowers, watches, bicycles, kitchen stand mixer. When my first hard drive died, took it apart. Hooked it up with the cover off to figure out what was wrong with it. Head was stuck on a scratch on the platter. Smoothed out the scratch and got the hard drive working again. Had some problems with the area I smoothed out but it worked in all other places.

When it came to understanding the Internet, Telecommunications, etc. I started reading things like RFCs, research papers at MIT, JSRs, ISO/ANSI drafts.

As I write this I am reminded of many of my students (I used to teach programming). During computer labs there was always someone who would ask me, "What would happen if I did XXX?" to which I always replied, "Try it and see." It always amazed me that most students would ask rather than just try it.

So if you want to be a good tester. Understand, Try, Hack.

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