I have tried testbook.com for practice purpose of different exams like ssc, banking etc. I have got good experience from it and help also. It helped me how to manage time for online exams. Then I have subscribed the for full time online exam which cost me very less amount of money. Its questions are very much standard and gives us good amount of experience as I had no experience of online exam.
I think every compititive exam appearing student should try the site atleast to gather some experience which is highly appreciated in the online exams.