Pull requests are very welcome! Make sure your patches are well tested and documented :)
If you are using a virtualenv, all you need is:
$ make test
You can also specify one or more test files to run:
$ make test which=tests/test_webdriver_firefox.py,tests/test_request_handler.py
You can pass which test files you want to run, separated by comma, to the which variable.
You can feel free to create and pull request new branches to Splinter project. When adding support for new drivers, we usually work in a separated branch.