Pytest smoke testing

It’s a good practice to test that some prerequisites are met before going further. This practice is sometimes called Smoke testing. When you have to setup an infrastructure either on a host or in docker images. In this case Pytest + testinfra is a terrific combo to perform this kind of testing.

A simple example

In a few lines of code you can easily test that some commands are working.

import logging
import pytest
from testinfra import host

logger = logging.getLogger(__name__)

cases = [
    ("Dumb", "echo 'dumb'"),
    ("Golang", "go version"),
    ("Python", "python --version"),
    ("Node", "node --version"),
    ("Failed", "Failed")

@pytest.mark.parametrize("name,command", cases, ids=[case[0] for case in cases])
def test_command(host, name, command):
    out = host.check_output(command)
    # Can use out to print the result of the command or to make something more clever"{name} [ OK ]")

Running this test will check that the commands run successfully.

$ pytest

=========== short test summary info ===========
FAILED[local-Failed] - AssertionError: Unexpected exit code 127 for CommandResult(command=b'Failed', exit_status=127, stdout=None, stderr=b'/bin/sh: Failed: command not found\n')
=========== 1 failed, 4 passed in 0.22s ===========

Going further

It’s only a simple example however it is interesting since it’s reproducible and will do the tedious work for you. Beyond this simple example this smoke test can

  • run, without modification, on various targets thanks to the implementation of pluggable backends: local machine, a docker image, several hosts through ansible, etc.,
  • be extended to integrate more complex checks thanks to the implementation of built-in modules.