Tests that run too long without output tends to break Travis builds.
This is typically the case when running code-coverage, so we need to
exclude a few test cases to ensure that the builds are stable.
This introduce a helper class that should be used to log things,
avoiding a lot of boilerplate code.
Also all output are made in /tmp folder instead of beside the script
itself. This is because there is a high chance that the folder containing
the script is not writtable by webserver. So using the /tmp folder
makes it more likely to works in a variety of setup.
