ApprovalTests.Python

Contents

• What can I use ApprovalTests for?
• Getting Started
  • What Are Approvals
  • New Projects
    • Minimal Example Tutorial
  • Adding to Existing Projects
• Overview
  • Example using pytest
  • Example using unittest
  • Example using CLI
    • Usage
    • Argument Definitions
• Reporters
• Support and Documentation
  • Missing Documentation?
  • Dependencies
    • Python
    • Required packages
    • Extra packages
• For developers
  • Weekly Ensemble
  • Pull Requests

Capturing Human Intelligence - ApprovalTests is an open source assertion/verification library to aid testing.
approvaltests is the ApprovalTests port for Python.

For more information see: www.approvaltests.com.

What can I use ApprovalTests for?

You can use ApprovalTests to verify objects that require more than a simple assert including long strings, large arrays, and complex hash structures and objects. ApprovalTests really shines when you need a more granular look at the test failure. Sometimes, trying to find a small difference in a long string printed to STDOUT is just too hard!
ApprovalTests solves this problem by providing reporters which let you view the test results in one of many popular diff utilities.

Getting Started

What Are Approvals

If you need to gain a better understanding or are new to this concept, start here.

New Projects

If you are starting a new project, we suggest you use the Starter Project. You can just clone this and go. It's great for exercises, katas, and green field projects.

Minimal Example Tutorial

If this is first time approvaltesting in python, consider starting here: Minimal Example Tutorial

Adding to Existing Projects

From pypi:

pip install approvaltests

Overview

Approvals work by comparing the test results to a golden master. If no golden master exists you can create a snapshot of the current test results and use that as the golden master. The reporter helps you manage the golden master.
Whenever your current results differ from the golden master, Approvals will launch an external application for you to examine the differences. Either you will update the master because you expected the changes and they are good, or you will go back to your code and update or roll back your changes to get your results back in line with the golden master.

Example using pytest

from approvaltests.approvals import verify


def test_simple() -> None:
    result = "Hello ApprovalTests"
    verify(result)

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Install the plugin pytest-approvaltests and use it to select a reporter:

pip install pytest-approvaltests
pytest --approvaltests-use-reporter='PythonNative'

The reporter is used both to alert you to changes in your test output, and to provide a tool to update the golden master. In this snippet, we chose the 'PythonNative' reporter when we ran the tests. For more information about selecting reporters see the documentation

Example using unittest

import unittest

from approvaltests.approvals import verify


class GettingStartedTest(unittest.TestCase):
    def test_simple(self) -> None:
        verify("Hello ApprovalTests")


if __name__ == "__main__":
    unittest.main()

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This example has the same behaviour as the pytest version, but uses the built-in test framework unittest instead.

Example using CLI

You can invoke a verify() call from the command line. This allows invoking python approvals from any other stack via subprocesses.

Usage

python -m approvaltests --test-id hello --received "hello world!"

or

python -m approvaltests -t hello -r "hello world!"

or

echo "hello world!" | python -m approvaltests -t hello

Argument Definitions

• --test-id or -t: Test identifier used to name the approved.txt and received.txt files for the test.

• --received or -r: The output of the program under test (a string) that is passed to the verify method.

  • stdin: Instead of providing a received argument, you may use stdin.

Reporters

A reporter controls how ApprovalTests handles a failing test result. The default behavior is to open a diff tool showing what you received vs what was approved. You can use this diff tool to change the approved to make the test pass the next time you run it. Reporters also have more advanced usages.

• Intro to reporters
• How to select a reporter
• How to create a custom reporter

Support and Documentation

• Documentation

• GitHub: https://github.com/approvals/ApprovalTests.Python

• ApprovalTests Homepage: http://www.approvaltests.com

Missing Documentation?

If there is documentation you wish existed, please add a page request to this issue.

Dependencies

Python

ApprovalTests is tested on the following Python versions: 3.10, 3.11, 3.12, 3.13, 3.14.

For older versions of Python, either:

• use an older version of ApprovalTests, or
• use TextTest, or
• hire us to help

Required packages

These dependencies are always required for approvaltests

pytest>=9.0.3
empty-files>=0.0.3
typing_extensions>=4.12.0

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Extra packages

These dependencies are needed if you are going to use the related functionality.
If you want the bare minimum you can use the pypi project approvaltests_minimal.

# For reporters.clipboard_reporter.ClipboardReporter
pyperclip>=1.5.29

# For approvals.verify_html()
beautifulsoup4>=4.9.0

# For pairwise_combinations.get_best_covering_pairs()
allpairspy>=2.1.0

# For utilities.logging.logging_approvals.verify_logging()
testfixtures >= 7.1.0, < 12
mock >= 5.1.0

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For developers

Weekly Ensemble

The best way to contribute is to join our weekly mob/ensemble.

Pull Requests

Pull requests are welcomed, particularly those accompanied by automated tests.

To run the self-tests: ./build_and_test.sh

This will run the self-tests on several python versions. We support python 3.10 and above.

All pull requests will be pre-checked using GitHub actions to execute all these tests. You can see the results of test runs here.