Run all std input test files in a folder and verify the result? (python)

I have a folder called tests that contains some files. The files are of two kinds, using an example: 01 and 01.a

01 is the input and 01.a is the expected output.

There are many pairs like this.

Normally, I would run program.py < tests/01 and manually check the output with 01.a.

Is there a way to automate this with many such pairs? Or is there a library that helps with this?