I was hired in a company for the title of Front-end Developer. I am qualified as because I have skills and experience with regards to doing front-end stuff. But it turns out that the work will be Full Stack. The employer was reasoning out that after your done with front-end task, I must do backend stuff as well so I would not be idle on may day's shift.

Is it my fault if I already done with my respective task and just mingle with random task of backend stuff that is not my real skills or forte?

I can understand and know PHP & MySQL, but I am not guaranteed to finish the task quickly compared to my backend counterpart in doing their task.

To cut the story short, they terminated my contract and claim that I am not performing well with my duties and responsibility, though most of the Front-end stuff I was assigned were already done and deployed.

There's no justice in this typical world of start-ups and noobie HR people that always one sided and they always say that it's their policy and they cannot do anything with regards to the incident happened to me.

Testdome.. is this a reliable test tool for developers? How sure you are qualified and fit to the job post if you pass all of the questions on this timer test?