Testing in the Web Environment
By Jeff Boes
February 13, 2009
Introduction
Testing is an important part of good software engineering practices. In fact, it can be said that it is at once the most important, and yet most neglected part of software engineering. Testing methodology for software engineering developed out of its hardware engineering roots: software was defined in terms of its inputs and outputs, and testing was similarly defined in terms of applied inputs and expected outputs.
However, software testing is more complex than that: this is because software almost always incorporates “state” or memory that affects subsequent operations. For instance, the following pseudocode:
if (VALUE is not defined) then VALUE := 1.0 fi FRACTION := 1.0 / VALUE
In this simple case, the code fragment will always operate correctly on the first execution, but subsequent executions may fail if VALUE is zero.
Testing web applications involves planning for this kind of memory, because in essence a web application runs within a larger program (the web server and perhaps the application server) and may inherit state from the environment, or indeed may preserve its own state from one page reference to the next.
In addition, web applications involve human …
browsers
Hot topic: user groups!
By Selena Deckelmann
February 10, 2009
Theodore T’so, Linux filesystem hacker, recently asked:
Do you attend or participate in a LUG? How active is it? What do you get out of participating in a LUG?
I attend and participate in my local LUG, PLUG. I’ve attended meetings since about 2000, and presented once to a group of about 45 people. They meet every month, and have an additional “advanced topics” meeting every month I’ve presented at as well.
What I get out of PLUG has changed over the years. First I was attending to meet other Linux enthusiasts and learn things. Now I go to meetings to see my friends, swap war stories, and to present on topics of interest to me. My goals are less about general networking, and more about directly connecting to, sharing information with and learning from people I already know, who are for the most part my friends and colleagues.
The comment thread on Ted’s post is kind of long, and there were lots of interesting comments. I decided to respond to some requests for howtos and weigh in with my opinion on the rise of user groups:
My experience has been that user groups (not just Linux User Groups) are exploding in number, but that the total number of people in each group is …
community
Test::Database Postgres support
By Greg Sabino Mullane
February 8, 2009
At our recent company meeting, we organized a ‘hackathon’ at which the company was split into small groups to work on specific projects. My group was Postgres-focused and we chose to add Postgres support to the new Perl module Test::Database.
This turned out to be a decent sized task for the few hours we had to accomplish it. The team consisted of myself (Greg Sabino Mullane), Mark Johnson, Selena Deckelmann, and Josh Tolley. While I undertook the task of downloading the latest version and putting it into a local git repository, others were assigned to get an overview of how it worked, examine the API, and start writing some unit tests.
In a nutshell, the Test::Database module allows an easy interface to creating and destroying test databases. This can be a non-trivial task on some systems, so putting it all into a module make sense (as well as the benefits of preventing everyone from reinventing this particular wheel). Once we had a basic understanding of how it worked, we were off.
While all of our tasks overlapped to some degree, we managed to get the job done without too much trouble, and in a fairly efficient manner. We made a new file for Postgres, added in all the required …
perl postgres git
David Mamet on software development
By Jon Jensen
February 7, 2009
I recently read the book True and False: Heresy and Common Sense for the Actor (1997) by David Mamet. (A gift from Uncle Steve. Thanks!) Mamet’s film The Spanish Prisoner is one of my favorites, and I liked Oleanna, Things Change, and Glengarry Glen Ross a lot too. Wait, looking over his writing credits at IMDb, I see I’d forgotten The Winslow Boy, State and Main, and Wag the Dog, which were good too.
Enough of the fanboyism. This little book of his is packed with what sounds like good advice for actors. Not having been an actor in anything more than a school play or two, I can only imagine, but I was surprised to find myself nodding in agreement during many passages because they applied so well to my field, software development.
I’ve selected a few quotations that seemed especially apt:
I was once at a marriage ceremony where the parties swore “to try to be faithful, to try to be considerate …” That marriage was, of course, doomed. Any worthwhile goal is difficult to accomplish. To say of it “I’ll try” is to excuse oneself in advance. Those who respond to our requests with “I’ll try” intend to deny us, and call on us to join in the hypocrisy—as if there were some merit in …
books development
NY Puppet Users Group meeting
By Steven Jenkins
February 4, 2009
Several of us from End Point attended the first NY Puppet Users Group meeting last night, and we had a great time. Brian Gupta and Larry Ludwig did an excellent time coordinating, even though the weather and the venue didn’t cooperate. After a little shuffling, we found ourselves at The Perfect Pint, where we had a large table in a fairly quiet room where we could meet each other and talk about Puppet.
The group was split fairly evenly between those who have used Puppet and those who are considering it: everyone there understood the need for solid configuration management (CM), so much of the discussions (at least at my end of the table) centered around
-
comparisons of different CM systems
-
challenges in getting Puppet on legacy systems (e.g., that may not even have Ruby)
-
features people would like to see in Puppet
-
how to make the business case for Puppet
All in all it was a great time, and I really appreciated Brian and Larry’s leadership, as well as their flexibility. Not only did they move the venue at the last minute to better accommodate the group, but they were super hosts in coordinating the date and time: several of us were only in NY for a short time, but they …
automation conference
Slony1-2.0.0 + PostgreSQL 8.4devel
By Josh Tolley
February 2, 2009
Many people use Slony to replicate PostgreSQL databases in various interesting ways. Slony is a bit tough to get used to, but works very well, and can be found in important places at a number of high-load, high-profile sites. A few weeks back I set up Slony1-2.0.0 (the latest release) with a development version of PostgreSQL 8.4, and kept track of the play-by-play, as follows:
Starting Environment
On this machine, PostgreSQL is installed from the CVS tree. I updated the tree and reinstalled just to have a well-known starting platform (output of each command has been removed for brevity).
jtolley@uber:~/devel/pgsql$ make distclean
jtolley@uber:~/devel/pgsql$ cvs update -Ad
jtolley@uber:~/devel/pgsql$ ./configure --prefix=/home/jtolley/devel/pgdb
jtolley@uber:~/devel/pgsql$ make
jtolley@uber:~/devel/pgsql$ make install
jtolley@uber:~/devel/pgsql$ cd ../pgdb
jtolley@uber:~/devel/pgdb$ initdb data
jtolley@uber:~/devel/pgdb$ pg_ctl -l ~/logfile -D data start
The –prefix option in ./configure tells PostgreSQL where to install itself.
Slony uses a daemon called slon to do its work, and slon connects to a database over TCP, so I needed to configure PostgreSQL to allow TCP connections …
postgres
Git it in your head
By Ethan Rowe
February 1, 2009
Git is an interesting piece of software. For some, it comes pretty naturally. For others, it’s not so straightforward.
Comprehension and appreciation of Git are not functions of intellectual capacity. However, the lack of comprehension/appreciation may well indicate one of the following:
-
Mistakenly assuming that concepts/procedures from other VCSes (particularly non-distributed “traditional” ones like CVS or Subversion) are actually relevant when using Git
-
Not adequately appreciating the degree to which Git’s conception of content and history represent a logical layer, as opposed to implementation details
CVS and Subversion both invite the casual user to basically equate the version control repository and all operations around it to the file system itself. They ask you to understand how files and directories are treated and tracked within their respective models, but that model is basically oriented around files and directories, period. Yes, there are branches and tags. Branches in particular are entirely inadequate in both systems. They don’t really account for branching as a core possibility that should be structured into the logical model itself; consequently, both systems …
git
Using cron and psql to transfer data across databases
By Greg Sabino Mullane
February 1, 2009
I recently had to move information from one database to another in an automatic function. I centralized some auditing information such that specific information about each database in the cluster could be stored in a single table, inside a single database. While I still needed to copy the associated functions and views to each database, I was able to make use of the new “COPY TO query”feature to do it all on one step via cron.
At the top of the cron script, I added two lines defining the database I was pulling the information from (“alpha”), and the database I was sending the information to (“postgres”):
PSQL_ALPHA='/usr/bin/psql -X -q -t -d alpha'
PSQL_POSTGRES='/usr/bin/psql -X -q -t -d postgres'
From left to right, the options tell psql to not use any psqlrc file found (-X), to be quiet in the output (-q), to print tuples only and no header/footer information (-t), and the name of the database to connect to (-d).
The cron entry that did the work looked like this:
*/5 * * * * (echo "COPY audit_mydb_stats FROM STDIN;" && $PSQL_ALPHA -c "COPY (SELECT *, current_database(), now(), round(date_part('epoch'::text, now())) FROM …postgres