I really love Quia.com, a paid testing software, that also allows students to play review games as well. It gives you great reports, and is easy to create questions. There is a volume discount if you get a group of teachers together.
Another online exam platform I have used is built into Canvas, a Learning Management System (LMS). I was able to create online exams, and it graded all the multiple choice and fill in the blank answers for me, and also made it easy to grade the short answer/essay type questions. However, this is just one part of the Canvas system, and you may not want to use a full LMS just for quizzes. A bonus, is that using Canvas is free.
If you are not willing to pay for a system, or want to use an LMS just for the quiz/test feature, a great resource is Google Forms. You can create a quiz using a form, and then use Flubaroo to grade it for you. Below are instructions on how to great a Google form, and how to use the Flubaroo Add-on.