See here: Openspeedtest on Docker on your router.
http://forum.mikrotik.com/t/openspeedtest-mikrotik-ready-container/162259/1
As always:
don’t use it to test the router itself.
Running this test does take away some resources so it will skew the results. ALways test thorugh a device, not using the device to be tested.
But you can use it to test all other internal connections in your network.