There is no direct instruction on how to delete your Speedtest account from the site, but the steps below will outline how to send a formal request to them to delete you off the system.
Log in your Speedtest account here.
Once at the landing page, scroll down until you see the link enclosed in the image below.
On the next page, you will be presented with options, from there you can select either of the 2 as shown below.
If you choose the first option, you are going to be routed to another page wherein you need to select the options indicated in the image below and fill in the necessary fields before hitting submit.
After clicking submit, a pop up will confirm your submission as shown in the image below.
After verifying your email, the deletion will already progress. The email you will receive will look like the one presented in the image below.
You will then receive this confirmation once they have deleted it.
The entire process can take up to a few days, keep monitoring your email for any updates.
For any other information regarding your account deletion, you may refer to the FAQ section below.