Showing posts from August, 2005

Managing DNS zone files with dnspython

I've been using dnspython lately for transferring some DNS zone files from one name server to another. I found the package extremely useful, but poorly documented, so I decided to write this post as a mini-tutorial on using dnspython.

Running DNS queries

This is one of the things that's clearly spelled out on the Examples page. Here's how to run a DNS query to get the mail servers (MX records) for

import dns.resolver

answers = dns.resolver.query('', 'MX')
for rdata in answers:
print 'Host',, 'has preference', rdata.preference To run other types of queries, for example for IP addresses (A records) or name servers (NS records), replace MX with the desired record type (A, NS, etc.)

Reading a DNS zone from a file

In dnspython, a DNS zone is available as a Zone object. Assume you have the following DNS zone file called

$TTL 36000 IN SOA hostmaster.example.…

Agile documentation in the Django project

A while ago I wrote a post called "Agile documentation with doctest and epydoc". The main idea was to use unit tests as "executable documentation"; I showed in particular how combining doctest-based unit tests with a documentation system such as epydoc can result in up-to-date documentation that is synchronized with the code. This type of documentation not only shows the various modules, classes, methods, function, variables exposed by the code, but -- more importantly -- it also provides examples of how the code API gets used in "real life" via the unit tests.

I'm happy to see the Django team take a similar approach in their project. They announced on the project blog that API usage examples for Django models are available and are automatically generated from the doctest-based unit tests written for the model functionality. For example, a test module such as tests/testapp/models/ gets automatically rendered into the 'Bare-bones model'

White-box vs. black-box testing

As I mentioned in my previous post, there's an ongoing discussion on the agile-testing mailing list on the merits of white-box vs. black-box testing. I had a lively exchange of opinions on this theme with Ron Jeffries. If you read my "Quick black-box testing example" post, you'll see the example of an application under test posted by Ron, as well as a list of back-box test activities and scenarios that I posted in reply. Ron questioned most of these black-box test scenarios, on the grounds that they provide little value to the overall testing process. In fact, I came away with the conclusion that Ron values black-box testing very little. He is of the opinion that white-box testing in the form of TDD is pretty much sufficient for the application to be rock-solid and as much bug-free as any piece of software can hope to be.

I never had the chance to work on an agile team, so I can't really tell if Ron's assertion is true or not. But my personal opinion is that t…