If you are looking for a way to bandwidth test from a PC through to a Mikrotik, here is your solution.
It supports RouterOS version 6.43 and newer. Advice from Mikrotik:
Please remember that Bandwidth Test uses a lot of resources. If you want to test real throughput of a router, you should run Bandwidth Test through the tested router not from or to it. To do this you need at least 3 devices connected in chain: the Bandwidth Test server, the router being tested and the Bandwidth Test client.