I applied online and after a few days they invited me to their premises to do three assessment tests including Bash scripting, Networking and one programming language of my choice(Java,C, C++, Python).
After the tests all candidates had to work together to to come up with a list of the most important items they would choose in a catastrophic scenario. Our scenario was that we were stranded on the moon after our spaceship crashed and we had to order some items according to their value and weight (oxygen tanks, matches(!), etc..).
Overall the entire process was fun and they were pretty casual with the candidates.