Today I've checked how Codility tests programmers. And it looks like a fun.
After you access a test (possibly to get certificate) you will have access to some simple web IDE where you will write your solution for the given problem. The task was some quite interesting algorithnic problem, to solve in 60 minutes.
It wasn't to hard but time limitation made it a nice challenge. I think it's quite good to test yourself and have some mental stretching.
Codility is used mainly as a recruitment tools for IT staff and that make me wondering how useful it is, especially to hire senior developers. Codility focuses on resolving algorithnic tasks, but in real life a developer must solve problems of much infrastructure complexity and I think that it might require different sets of skills.
But obviously it's nice tools to verify some basic programming skills of possible junior developers.
And in the end, this is my Certificate gained in Codility:
