Code correctness, and testing strategies

David wizzardx at gmail.com
Wed Jun 11 10:39:49 CEST 2008


Thanks again for an informative reply :-)

I finished that small app I mentioned last time (before reading the
the last reply to this thread). A few points (apologies for the
length):

I added a few integration tests, to test features which unit tests
weren't appropriate for. The main thing they do is call my main
object's 'run_once()' method (which iterates once) instead of 'run()'
(which runs forever, calling run_once() endlessly), and then check
that a few expected things took place during the iteration.

Those integration tests helped me to find a few issues. There were a
few 'integration' tests which were actually acceptance/functional
tests because integration tests weren't good enough (eg: run script in
unix daemon mode and check for pid/lock/etc files). I left those under
integration because it's annoying to change to 3 different directories
to run all of the tests. I should probably split those off and
automate the testing a bit more.

After doing all the automated tests, I did some manual testing (added
'raise UNTESTED' lines, etc), and found a few more things. eg, that
one of my (important) functions was being unit tested but not ever
being run by the main app. Fixed it with BDD, but it is something I
need to be aware of when building bottom-up with BDD :-) Even better:
develop top down also, and have acceptance tests from the start, like
you mentioned before.

Another thing I found, was that after installing on a test system
there were more failures (as expected). Missing depedencies which had
to be installed. Also Python import errors because the files get
installed to and run from different directories than on my
workstation. Not sure how I would use BDD to catch those.

Finally - I didn't use BDD for the debianization (checking that all
the shell scripts & control files work correctly, that the debian
package had all the files in the correct places etc). I figured it
would be too much trouble to mock the Debian package management
system, and all of the linux utilities.

Should a BDD process also check 'production' (as opposed to 'under
development') artifacts? (installation/removal/not being run under a
version control checkout directory/missing dependancies/etc)?

In the future I'll probably create 'production' acceptance tests (and
supporting utilities) following BDD before debianization. Something
automated like this:

1) Build the installer package from source
2) Inspect the package and check that files are in the expected places
3) Package should pass various lint tests
4) Install the package under a chroot (reset to clear out old deps, etc)
5) Check that files etc are in the expected locations
6) Run functional tests (installed with the package) under the chroot
7) Test package upgrades/removal/purges/etc under the chroot.

There are a few existing Debian utilities that can help with this.

On Wed, Jun 11, 2008 at 4:36 AM, Ben Finney
<bignose+hates-spam at benfinney.id.au> wrote:
> David <wizzardx at gmail.com> writes:
>

[...]

>
>> Does this mean that you leave out the formal 'integration' and
>> 'systems' testing steps? By actually running the app you are doing
>> those things more or less.
>
> I'm not sure why you think one would leave out those steps. The
> integration and systems tests should be automated, and part of some
> test suite that is run automatically on some trigger (such as every
> commit to the integration branch of the version control system).
>

It sounded that way because when I asked about integration tests
originally, you said to use approval testing. Which seems to
completely skip the automated 'integration' and 'systems' testing
steps I was expecting.

>
> A Python distutils 'setup.py' is a very common way to set up the build
> parameters for an application.
>

I don't make setup.py, because my work projects are always installed
via apt-get onto Debian servers. setup.py is a bit redundant and less
functional for me :-)

Might be a bad practice on my part. Usually you start with a
non-Debian-specific install method. Which then gets run to install the
files into a directory which gets packaged into a Debian installer. I
cheat with Python apps because I'm both the upstream author and the
Debian maintainer. I setup my Debian control files so they will copy
the .py files directly into the packaged directory, without running
any non-Debian-specific install logic.

I should probably have a setup.py anyway... :-)

>> But I will be making a Debian installer a bit later.
>
> That's an important part of the build process, but you should write
> (and test via your automated build process) a 'setup.py' before doing
> that.

Should I have a setup.py if it won't ever be used in production?

>
>> I've considered setting up a centralised build server at work, but
>> currently I'm the only dev which actually builds & packages
>> software, so it wouldn't be very useful.
>
> It's extremely useful to ensure that the automated application build
> infrastructure is in place early, so that it is easy to set up and
> automate. This ensures that it actually gets done, rather than put in
> the "too hard basket".

Thanks for the advice. I'll look into setting it up :-)

At the moment I have ad-hoc projects in my home directory, each with
it's own git repo. There's at least 100 of them. Usually I run a local
script to build deb files from one of those dirs, and push them to our
internal debian repo. I'll setup a system where public git repos (with
hook scripts) get setup on the build server. Then I'll push my changes
to the server when I want a package to be built & uploaded. I also
want the same system on my workstation for testing, and in case there
are network problems.

>
> The benefits are many even for a single-developer project: you have
> confidence that the application is simple to deploy somewhere other
> than your development workstation, you get early notification when
> this is not the case, you are encouraged from the start to keep
> external dependencies low, your overall project design benefits
> because you are thinking of the needs of a deployer of your
> application, and so on.

I already think this way because I manage our installation
infrastructure (I have a developer hat, a package maintainer hat, and
a release manager hat). But it might be useful for other devs in the
future, if I can get them to use the sysem ;-) Also so they can make
new packages etc while I'm on leave without having to use my
workstation :-) Hasn't happened yet. Usually they would just SCP
updated PHP files into production without using Debian installers.
Their work is important, but it doesn't perform any critical function
:-) (as in bugs = lost mega bucks per minute).

>> We do have other devs (PHP mostly), but they don't even use version
>> control :-/.
>
> Fix that problem first. Seriously.
>

I've tried a few times, but haven't succeeded yet. It's not an easy
concept to sell to people who aren't interested, and there is more
work involved than simply hacking away at source and making occasional
copies to a new 'bpk' or 'old' sub-directory.

There have been a few cases where the devs were working on code, when
clients came in and needed to see an earlier version (also not in
production yet). I've saved their bacon by restoring the correct
version from our daily backups. We didn't have much in the way of
backups either before I set them up :-)

David.



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