Wednesday, September 26, 2007

Roy Osherove book on "The art of unit testing"

Just found out from Roy Osherove's blog that his book on "The Art of Unit Testing" is available for purchasing online -- well, the first 5 chapters are, but then you get the next as they're being published. Roy uses NUnit to illustrate unit testing concepts and techniques, but that shouldn't deter you from buying the book, because the principles are pretty much the same in all languages. I'm a long time reader of Roy's blog and I can say this is good stuff, judging by his past posts on unit testing and mock testing techniques.

Wednesday, September 19, 2007

Beware of timings in your tests

Finally I get to write a post about testing. Here's the scenario I had to troubleshoot yesterday: a client of ours has a Web app that uses a java applet for FTP transfers to a back-end server. The java applet presents a nice GUI to end-users, allowing them to drag and drop files from their local workstation to the server.

The problem was that some file transfers were failing in a mysterious way. We obviously looked at the network connectivity between the user reporting the problem initially and our data center, then we looked at the size of the files he was trying to transfer (he thought files over 10 MB were the culprit). We also looked at the number of files transferred, both multiple files in one operation and single files in consecutive operations. We tried transferring files using both a normal FTP client, and the java applet. Everything seemed to point in the direction of 'works for me' -- a stance well-known to testers around the world. All of a sudden, around an hour after I started using the java applet to transfer files, I got the error 'unable to upload one or more files', followed by the message 'software caused connection abort: software write error'. I thought OK, this may be due to web sessions timing out after an hour. I did some more testing, and the second time I got the error after half an hour. I also noticed that I let some time pass between transfers. This gave me the idea of investigating timeout setting on the FTP server side (which was running vsftpd). And lo and behold, here's what I found in the man page for vsftpd.conf:

The timeout, in seconds, which is the maximum time a remote client may spend between FTP commands. If the timeout triggers, the remote client is kicked off.

Default: 300

My next step was of course to wait 5 minutes between file transfers, and sure enough, I got the 'unable to upload one or more files' error.

Lesson learned: pay close attention to the timing of your tests. Also look for timeout settings both on the client and on the server side, and write corner test cases accordingly.

In the end, it was by luck that I discovered the cause of the problems we had, but as Louis Pasteur said, "Chance favors the prepared mind". I'll surely be better prepared next time, timing-wise.

Thursday, September 13, 2007

Barack Obama is now a connection

That's the message I see on my LinkedIn home page. How could this be possible, you ask? Well, yesterday I checked out my home page, and I noticed the 'featured question of the day' asked by Barack Obama himself (of course, the question was "how can the next president better help small businesses and entrepreneurs thrive".) A co-worker decided to send a LinkedIn invite to Barack. A little while later, he got the acceptance in his inbox. I followed his example, just for fun, and what do you know, I got back the acceptance in a matter of SECONDS, not even minutes! It seems that B.O. has set his LinkedIn account to accept each and every invite he gets. I guess when you're running for president, every little statistic counts. He already has 500+ connections, and I'm sure the time will come when he'll brag to the other candidates that his LinkedIn account is bigger than theirs.

The bottom line is that YOU TOO can have Barack as your connection, if only to brag to your friends about it.

Wednesday, September 12, 2007

Thursday, September 06, 2007

Security testing book review on Dr. Dobbs site

I wrote a review for "The Art of Security Testing" a while ago for Dr. Dobbs. I found out only now that it's online at the Dr. Dobbs's Portal site. Read it here.

Wednesday, September 05, 2007

Weinberg on Agile

A short but sweet PM Boulevard interview with Jerry Weinberg on Agile management/methods. Of course, he says we need to drop the A and actually drop 'agile' altogether at some point, and just talk about "normal, sensible, professional methods of developing software." Count me in.

Tuesday, September 04, 2007

Jakob Nielsen on fancy formatting and fancy words

Just received the latest Alertbox newsletter from Jakob Nielsen. The topic is "Fancy Formatting, Fancy Words = Ignored". I'd have put 2 equal signs in there, but anyway....The 'ignored' in question is your web site, if you're trying to draw attention to important facts/figures by using red bold letters and pompous language. Nielsen's case study in the article is the U.S. Census Bureau's homepage, which displayed the current population of the US in big red bold letters, and called it "Population clock". As a result, users were confused as to the meaning of that number, and what's more, they didn't bother to even read the full number, because they thought it's an ad of some sort. Interesting stuff.

Modifying EC2 security groups via AWS Lambda functions

One task that comes up again and again is adding, removing or updating source CIDR blocks in various security groups in an EC2 infrastructur...