Testing script output

I have a Python script that accepts one input (a text file): ./myprog.py file.txt. The script outputs a string based on the given input.

I have a set of test files that I would like to test my program with. I know the expected output for each file and want to make sure my script produces the correct output for each file.

What is the generally accepted way to do this type of testing?

I was thinking of using Python's unittest module as the testing framework, and then running my script through subprocess.check_output(stderr=subprocess.STDOUT), capturing stdout and stderr, and then doing a unittest assertEqual to compare the actual and expected strings. I want to make sure I'm not missing some nicer solution.