How to build an Isolated Drupal instance for testing In order to run DrupalWebTests on travis-ci, I need to build a new Drupal instance where these tests are ran.

Typically, one runs these tests with drush -l http://localhost.example test-run SomeTest

This, however, assumes Drupal installed, being served on http://localhost.example (a webserver) and it being connected to a database as set in settings.php, having simpletest enabled.

Typically, this means installing MySQL, Apache and installing and configuring Drupal. Those are heavy depedencies and doing so for each test-case or even just every build, will require a lot of overhead; a build server like Travis will need to install these servers for each test-run.

Drush has drush run-server to run a lightweight server. Drupal can run off a sqlite database, which would be extremely usefull for these tests.

Moreover: as far as I can make out, the actual web-tests are not ran from that Drupal-instance at http://localhost.example, but get a clean build and isolated database (as should be, when testing). It appears that the Fully-functional Drupal at http://localhost.example is merely used as bootstrap for the web-tests. 

Can I circumvent that bootstrap in some way?

And if not, what is a quick and easy way to get a Drupal installed and serving with as little dependencies (like Apache/Nginx, MySQL etc) as possible?

Also note that I am running Travis already for tagadelic, but so far, only for the phpunit tests. I want to extend this to run the DrupalWebTests there as well.
You could just use different git branches to isolate your code tests.

git checkout -b iss_tst1
&lt;make changes&gt;
git add &lt;changes&gt;
git commit -m "my new changes" &lt;changes&gt;

git checkout -b iss_tst2
&lt;make changes&gt;
git add &lt;changes&gt;
git commit -m "other new independent changes" &lt;changes&gt;


Then you should be able to run independent tests on each branch.