TestMy.net is currently only testing your single file transfer performance (on upload). This is close to what you'll see if you try and upload a single file somewhere. This also shows you what kind of streaming quality your connection is capable of. If you tried to stream over 70 Mbps, you'd probably have issues.
My new beta is built around a multithread upload test. Join us in testing >> https://testmy.net/ipb/topic/34612-beta-testers-welcome/
The multithread upload test will help you see how fast you are when you combine multiple transfers together. Comparing the two tests helps you understand your connection better.
Little Banshee got a reaction from CA3LE in Why is my upload so much slower here than speedtest?