unit test build files

Question

What are the best policies for unit testing build files?

The reason I ask is my company produces highly reliable embedded devices. Software patches are just not an option, as they cost our customers thousands to distribute. Because of this we have very strict code quality procedures(unit tests, code reviews, tracability, etc). Those procedures are being applied to our build files (autotools if you must know, I expect pity), but if feels like a hack.

Uh... the project compiles... mark the build files as reviewed and unit tested.

There has got to be a better way. Ideas?

Answer 1

Here's the approach we've taken when building a large code base (many millions of lines of code) across more than a dozen platforms.

• Makefile changes are reviewed by the build team. These people know the errors people tend to make in our build environment, and they are the ones who feel the brunt of it when a build breaks, so they're motivated to find issues.
• Minimize what needs to go in a Makefile, so there are fewer opportunities for error. We have a layer on top of make, that generates the Makefile. A developer just has to indicate in the higher-level file, using tags, that for example a given target is a shared library or a unit test. Usually a target is defined on one line, which then results in multiple settings/targets in the generated Makefile. Similar things could be done with build tools like scons that allow one to abstract away things like platform-specific details, making targets very simple.
• Unit tests of our build tool. The tool is written in Perl, so we use Perl's Test::More unit test framework there to verify that the tool generates the correct Makefile given our higher-level file. If we used something like scons instead, I'd use their testing framework.
• Unit tests of our nightly build/test scripts. We have a set of scripts that start nightly builds on each platform, run static analysis tools, run unit tests, run functional tests, and report all results to a central database. We test the various scripts individually, mostly using the shunit2 unit-testing framework for sh/bash/ksh/etc.
• End-to-end tests of our build/test process. I am working on an end-to-end test that operates on a tiny source tree rather than our production code, since the latter can take hours to build. These tests are mainly aimed at verifying that our build targets still work and report results into our central database even after, for example, upgrading our code coverage tool or making changes to our build scripts.

Answer 2

Have your build file to compile a known version of your software (or simpler piece of code that is similar from a build perspective) and compare the result obtained with your new build tools to a expected result (built with a validated version of the build tools).