If you are looking for a good online typing test to increase productivity, one that you may try is typeonline.co.uk
This website features three practice typing test to improve your typing test, there are a number of websites who offer free typing speed test, but I find the website simple but covers the practice test you may need. This is beneficial not only for writers, but also for kids, to test job applicants, for students, and other field of work.
First is typing test with words, test with numbers, and the test of words and numbers. Aside from these test, it also features safety information related to typing injuries and how to avoid it. There typing lessons with words, numbers, copy practice lessons. If you are serious with your improvement, take the lessons, speed test, monitor and evaluate your progress.