How to test input via subprocess.Popen with data from file

[Dieter Maurer]

Loris Bennett wrote at 2022-3-11 07:40 +0100:
> ... I want to test the parsing ...
>Sorry if I was unclear but my question is:
>
>Given that the return value from Popen is a Popen object and given that
>the return value from reading a file is a single string or maybe a list
>of strings, what should the common format for the argument which is
>passed to the actual parsing function be?

What methods (of its input argument) does the parsing use?
If it uses `Popen` methods, then you pass a `POpen` object;
if it uses only (typical) file methods, then you pass a file object;
if it assumes its input to be a (line) interator, you pass
a (line) iterator (such as a "file" object).

I would design the parsing that it makes as few assumptions
about its input as possible -- to ease testing
and increase the chance for reuse.

That said, I would not design it to work with `Popen` objects
but likely to have a line iterator as input.