In short, I have written a Python program to write a series of commands to a serial device I'm working with, and I want to make sure they're working in the way I want them to.
For sure, no device connected means no response/nothing to read...
Did you consider trying a serial port sniffer, if you google for serial port sniffer, you'll find more than you need.
Connect any serial device and sniff what you send.
Is there a way to view what is being written on serial from a Python script without connecting a device?