I sure would love to have that speed...
It does bug me also that most people I've encountered that sees a much lower speed on TestMy automatically puts the fault at TestMy instead of their ISP not being able to measure their connection as I've lost count of the number of times I've tried explaining why the two sites give such different results. Here, I'm talking about speeds in the 50Mbps to 100Mbps region where TestMy may throw up 6 to 8Mbps while Speedtest.net throws up 40 to 50Mbps, such as what I see on my 4G connection from time to time.
The primarily reason is that Speedtest.net always runs its test multi-threaded and discards the 30% lowest readings during its test, while TestMy makes a linear connection to the Test server and factors in the entire test including dips in its test result. So when my 4G connection is showing a test result of 6Mbps, I know that ~750KB/s is what to expect from individual downloads and generally that's the case, even when Speedtest.net claims I'm getting 40+Mbps. This is especially important with streaming services as a Speedtest.net result of let's say 20Mbps does not necessarily mean that YouTube can stream video at 6Mbps for 1080p video.
Another way to double-check your connection is with a download from Leaseweb's test file set. Start the download of a large file (e.g. 1000MB sample) and wait a few seconds for the transfer rate figure settles. Multiply this figure by 8 to convert to Mbps and you should get what your ISP is sustaining in this transfer. For me, this generally matches up with what I get with the TestMy UK and Germany servers nearest to me and it's very unlikely that the bottleneck along the route is at Leaseweb's end.