Very unprofessional behavior.
From the beginning. I received a task in the form of PDF. The task description was short and not descriptive enough. It has been said that I got up to 24 hours to finish. I spent 6 hours on coding the project and sent them back before deadline. Used cmake and implemented couple tests using googletest. After that they went silent for a week or so, I contacted them what's going on and still nothing. After another week I contacted again what's going on and received a reply that my temper is bad and the solution I provided was not as they expected and they thank me, because I'm not kind of person they would like to work with. I believe they rejected me because I did not wanted to wait 3 or so weeks to get an answer and actively asked questions.
Overall: don't waste time for them.