Without a doubt, https://www.speedtest.net/ is the most used speed test checker out there. However, what people don't realize is that they are actually not the best....
Since the IP addresses that are allocated to the dedicated servers that we run your VPS machine's on are located in Buffalo, but the actual server is hosted in another datacenter (for example, our Dallas datacenter location), Speedtest.net doesn't have smart enough technology to realize that the server is in our Dallas datacenter, so they do a speedtest from our Buffalo location. That's a very long distance, and it explains why you see bad speed test results if you have a VPS in our Dallas location (refer to this article: https://support.speedtest.net/hc/en-us/articles/203845660-How-do-I-correct-my-location-)
What can you do?
The only thing to do so you can see your TRUE speed is to test on another site. https://testmy.net/download has been reliable showing 700+ Mbps speeds for us. Just do a Google search for "online download speed test" and try any number of sites... if you see just ONE site that has 700+ Mbps speeds (and you will), then you know that the problem is not with our server's speeds, but rather with the test servers you are running the speed tests on.
Refer to this article for more information on why speed tests are unreliable, but you are truly on a 1 Gbps network line: Why Do I Get Low Speed Test Results?
They have their very old version that runs on Adobe Flash, and their new Beta version that runs without Flash. Firefox doesn't even support Flash anymore, that tells you how outdated that technology is. Well, that also affects your speed test results. Here's proof from the same Windows VPS server of speed tests I ran, one on Chrome (which uses Adobe Flash) and one on Firefox (which uses the new Beta version)
So, if you're going to test our VPS's speed, please refrain from using Chrome that uses old technology and use Firefox (which is preinstalled on your VPS already).