Skip to main content

Useful helpers for writing tests for your Python CLI program.

Project description

cli-test-helpers Latest version on PyPI

Build status Python versions Software license

Useful helpers for writing tests for your Python CLI program.

Writing tests for a command line interface (CLI) tool may not seem strictly straight-forward when you think in terms of unit tests. Especially, when you use the argparse module or the click package, control of the application entry point is a bit taken away from you.

But it’s not all that bad. This package is here to help. The examples give you some guidance on how to get started, and the helpers allow you to deal with common cases, such as mocking CLI arguments and environment variable values.

Installation

pip install cli-test-helpers

Preferrably, though, you add cli-test-helpers as a dependency to your Tox environment (see example).

Usage

Let’s assume you use pytest for running your tests, which is certainly a good idea. Your CLI program is called foobar. You have prepared a setup.py with a CLI entrypoint. For the tests you have prepared a tests/ folder (outside of foobar/, because you don’t want your tests to be packaged up with your application code). Then your directory layout looks somewhat like our example.

Functional tests

Start with a simple set of functional tests:

  • Is the entrypoint script installed? (tests the configuration in your setup.py)

  • Can this package be run as a Python module? (i.e. without having to be installed)

  • Is command XYZ available? etc. Cover your entire CLI usage here!

This is almost a stupid exercise: Run the command as a shell command and inspect the status code of the exiting process (see example). The trick is that you run a non-destructive command, e.g. by using the usual --help option of every command. This should cover your entire CLI user interface definition.

Unit tests

Then you’re ready to take advantage of our helpers.

ArgvContext allows you to mimic the use of specific CLI arguments:

def test_cli_command(mock_command):
    """Is the correct code called when invoked via the CLI?"""
    with ArgvContext('foobar', 'baz'):
        foobar.command.baz()

    assert mock_command.call_count == 1

EnvironContext allows you to mimic the presence of environment values:

def test_fail_without_secret():
    """Must fail without a ``SECRET`` environment variable specified"""
    message = "Environment value SECRET not set."

    with EnvironContext(SECRET=None):
        with pytest.raises(SystemExit, match=message):
            foobar.command.baz()
            pytest.fail("CLI doesn't abort with missing SECRET")

See example.

TDD

Remember to stick to the test-driven mantra:

  1. Write one line of test code. Make the test fail.

  2. Write one line of application code. Make the test pass.

  3. Goto 1.

Project details


Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Source Distribution

cli-test-helpers-1.0.0.tar.gz (17.3 kB view details)

Uploaded Source

Built Distribution

cli_test_helpers-1.0.0-py2-none-any.whl (16.3 kB view details)

Uploaded Python 2

File details

Details for the file cli-test-helpers-1.0.0.tar.gz.

File metadata

  • Download URL: cli-test-helpers-1.0.0.tar.gz
  • Upload date:
  • Size: 17.3 kB
  • Tags: Source
  • Uploaded using Trusted Publishing? No
  • Uploaded via: twine/1.15.0 pkginfo/1.5.0.1 requests/2.22.0 setuptools/41.4.0 requests-toolbelt/0.9.1 tqdm/4.36.1 CPython/2.7.15

File hashes

Hashes for cli-test-helpers-1.0.0.tar.gz
Algorithm Hash digest
SHA256 eedff2c4f754f250042702089219dc29827b2c8d53a7d2dd1c3d4ce3d05af8df
MD5 9eda53e40f8fe91a79e3801f81121430
BLAKE2b-256 b5bfa7326bb5b54c78ec67eed7c1e9341a67c24ef09e13814164f7b30f1b03a0

See more details on using hashes here.

File details

Details for the file cli_test_helpers-1.0.0-py2-none-any.whl.

File metadata

  • Download URL: cli_test_helpers-1.0.0-py2-none-any.whl
  • Upload date:
  • Size: 16.3 kB
  • Tags: Python 2
  • Uploaded using Trusted Publishing? No
  • Uploaded via: twine/1.15.0 pkginfo/1.5.0.1 requests/2.22.0 setuptools/41.4.0 requests-toolbelt/0.9.1 tqdm/4.36.1 CPython/2.7.15

File hashes

Hashes for cli_test_helpers-1.0.0-py2-none-any.whl
Algorithm Hash digest
SHA256 ed1bbae7031f66339510076450ad4ccff918ffadf565f7dfa884f148cb674d00
MD5 f5858821f887c8f31db82e3476b6a43a
BLAKE2b-256 19692df351e8e099b562ff17bda3a8e9d9ba09d283165119d0a826335670d604

See more details on using hashes here.

Supported by

AWS Cloud computing and Security Sponsor Datadog Monitoring Fastly CDN Google Download Analytics Pingdom Monitoring Sentry Error logging StatusPage Status page