pytest-subprocess is a pytest plugin to fake subprocess.

The plugin adds the fake_process fixture (and fp as an alias). It can be used
it to register subprocess results so you won't need to rely on the real
processes. The plugin hooks on the subprocess.Popen(), which is the base for
other subprocess functions. That makes the subprocess.run(), subprocess.call(),
subprocess.check_call() and subprocess.check_output() methods also functional.