TDC: Test-driven configuration

Is there anything more terrible than getting a phone call and someone complaining about a printer that does not work?
Yes, you have to admit that something is broken and you are not able to repair it immediately.

So, how can you avoid such situations?

For some time now in software development you can find a concept called TDD (Test-driven development). Basically you repeat three steps:

  1. develop a test for a new function; as this function does not exist yet, this test has to fail in the beginning
  2. develop the function; the aim in this step is to pass the test and don’t break any other test
  3. refactor code; code can be optimized and improved, do not break any test in this step

Would it be possible to introduce something similar for the configuration of computers/software? Analogous to TDD one could call this TDC (Test-driven configuration).

There is only one relevant Google hit for this keyword. It is an article written by David Lutz from 2011. Other Keywords like “Test-driven Sysadmin” show among others some slides of Johan van den Dorpe which led to Behavioral Driven Development (BDD) and some software called cucumber. Another software that is mentioned is babushka.

Unfortunately these software does not fit into existing solutions for configuration management like puppet or testing like nagios. They are independent software packages that need their own configuration, which might lead to some kind of synchronization error between both worlds.

Is this really such a weird idea that just a few people thought about this?

Anyway, I will also give it a try and I am curious where all of this is going.

In Wikipedia there is a huge list of configuration management software. As all my systems are running on Debian, I will limit my work on software that is part of Debian and has an arbitrary popcon value of at least 1000. So my main target will be puppet. Other software I will look into are ansible and salt. Due to their trademark policy, chef won’t be part of Debian soon, so I won’t consider it.

In Wikipedia one can also see an even bigger list of network monitoring system. My main target on this list will be nagios. I will also look into zabbix and prometheus.

Finally I found a tweet from Jaana Dogan:
“Configuration testing is quite underrated in an industry where the majority of work is becoming configuration.”

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