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

[Dieter Maurer]

Loris Bennett wrote at 2022-3-10 13:16 +0100:
>I have a command which produces output like the
>following:
>
>  Job ID: 9431211
>  Cluster: curta
>  User/Group: build/staff
>  State: COMPLETED (exit code 0)
>  Nodes: 1
>  Cores per node: 8
>  CPU Utilized: 01:30:53
>  CPU Efficiency: 83.63% of 01:48:40 core-walltime
>  Job Wall-clock time: 00:13:35
>  Memory Utilized: 6.45 GB
>  Memory Efficiency: 80.68% of 8.00 GB
>
>I want to parse this and am using subprocess.Popen and accessing the
>contents via Popen.stdout.  However, for testing purposes I want to save
>various possible outputs of the command as text files and use those as
>inputs.

What do you want to test? the parsing? the "popen" interaction?
You can separately test both tasks (I, at your place, would do this).

For the parsing test, it is not relevant that the actual text
comes from an external process. You can directly read it from a file
or have it in your text.

In my view, you do not need a test for the `Popen` interaction:
if it works once, it will work always.