While speedtest.net is not always the most reliable service to test your internet line speed, you should always get almost full speed if you test to a local sever in your area.
Remember that you need to make sure to unplug all other devices while testing the speed, as other devices can influence the speed you get. For example, if you are testing the speed of the internet but your wife is streaming the latest episode of House of Cards in 4k on Netflix, then it will definitely affect the speed you are getting.
Remember that WiFi will slow down your speed test as the signal may be poor or you may find that the WiFi network gets plenty of interference. Remember that a simple thing like turning on your microwave can interfere with your wifi signal. The more interference you get on your wifi signal and poor signal strength are the biggest contributors to slow / poor internet speeds.
While it is not always possible RocketNet advises for the best experience to always use a CAT6 or CAT5e cable where possible.