The only driver's test offered online is the permit test for the State of Florida as of 2015. All other tests in Florida and other states are required to be completed in person at the testing center. The testing centers in most states do offer practice tests online and study guides, some of which are printable.
While drivers cannot take the test online, they can schedule their written and driving tests online with some state facilities. This is a good way to avoid the long wait times and having to go back multiple times in order to get a license, which is especially important for new drivers and can help with testing nerves.