Python Testing with pytest

Testing a Simple Python Script

Let’s start with the canonical coding example, Hello World!:

ch12/script/hello.py

print("Hello, World!")

The run output shouldn’t be surprising:

$ cd /path/to/code/ch12/script
$ python hello.py
Hello, World!

Like any other bit of software, scripts are tested by running them and checking the output and/or side effects.

For the hello.py script, our challenge is to (1) figure out how to run it from a test, and (2) how to capture the output. The subprocess module, which is part of the Python standard library,^[42] has a run() method that will solve both problems just fine:

ch12/script/test_hello.py

from subprocess import run


def test_hello():
    result = run(["python", "hello.py" ...