If you want to do an ongoing speedtest with graphs for up- and download, forget about the web-based tools like speedtest.net and fast.com - those are nice if you are on a mobile phone. These speedtests as a service will not show you continuous graphs (which sometime you might want to have if you are tweaking your network).
On such occasions, your *nix shell yields better tooling!
First, fire up a Terminal and start
nload to view network traffic.
If you are on macOS, you can also use the graphical tool
Then, in a second Terminal, start a permanent upload or download with the following commands:
ssh email@example.com "cat /dev/urandom" > /dev/null
cat /dev/urandom| ssh firstname.lastname@example.org "cat > /dev/null"
Note that depending on your
ssh configuration, you might need to
disable compression on the client or server side.