Does BAFO "BF-810 USB to Serial Adapter (DB9)" supports full serial port?
When RS-232 cables were everywhere, a standard piece of test equipment was a small block with D connectors on the ends and LEDs on one face labeled for each significant signal. A quick check shows that such devices are still made, here's a typical example available for about US$11.

I also have a variety of null-modem, gender changers, and 9 pin to 25 pin in my toolbox.

A device like this gives quick confirmation that only the expected pins are driven when attached to each device, and can be left inline to verify that the data and handshake signals are in use. 

This does only confirm that the output pins have signal conditioning. It ought to be safe to assume that if TXD is driven, then RXD can receive, and similarly for RTS/CTS and DSR/DTR.