pytest-snapshot

library0.9.0pypypi✓ verified 25d ago

pytest-snapshot is a plugin for snapshot testing with pytest. It enables developers to compare current test outputs (e.g., data structures, HTML, JSON) against a pre-recorded 'snapshot', failing tests if a mismatch occurs. The current version is 0.9.0, and it maintains an active release schedule with regular minor and patch updates.

testing

pip install pytest-snapshot

github ↗package ↗

INSTALL

IMPORT

SIG · PYTEST-SNAPSHOT

pytest-snapshot

testingpythonv0.9.0

Install

2.6s avg

Import

—

Disk

30MB

Pass rate

10/ 10

Env Coverage10 / 10

glibc

3.9–3.13

musl

3.9–3.13

Install & Compatibility

Where this runs

tested against v0.9.0 · pip install

no network on importno background threads

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

py 3.10–3.95 runs

installs and imports cleanly · install 0.0s · import 0.000s · 31.1MB

glibc

py 3.10–3.95 runs

installs and imports cleanly · install 2.6s · import 0.000s · 32MB

30MB installed

● package 30MB

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

snapshot

✓ def test_example(snapshot): # ... use snapshot.assert_match(data, 'snapshot_name.json') ...

The 'snapshot' fixture is automatically provided by the pytest-snapshot plugin to any test function that declares it as an argument. No explicit 'import' statement from 'pytest_snapshot' is needed to use the fixture.

This quickstart demonstrates how to use the `snapshot` fixture within a pytest function to test a Python dictionary. The first execution with `--snapshot-update` creates the baseline snapshot; subsequent runs verify that the data structure remains consistent.

import pytest def test_data_structure(snapshot): # Simulate some data generated by your application data = { "id": 101, "name": "Sample Product", "config": { "enabled": True, "features": ["search", "filter"] } } # The snapshot file (e.g., my_product_snapshot.json) will be created # or updated relative to the test file's directory. snapshot.assert_match(data, "my_product_snapshot.json") # To run this test: # 1. Save the code as `test_product.py`. # 2. Run `pytest --snapshot-update` in your terminal to create or update the initial snapshot. # 3. Subsequent runs of `pytest` (without `--snapshot-update`) will compare against the saved snapshot.

Debug

Known issues

gotchaTo create or update snapshots, you MUST explicitly run pytest with the `--snapshot-update` CLI flag. Without this flag, tests will fail if snapshots are missing or do not match, but new snapshots will not be generated or updated.

fix

Always use `pytest --snapshot-update` when you intend to create or modify snapshot files.

affects: All versions

breakingPython 2 support was officially dropped in version 0.5.0. pytest-snapshot now requires Python 3.5 or newer to function.

fix

Ensure your testing environment uses Python 3.5 or a more recent version.

affects: >=0.5.0

breakingBeginning with version 0.5.0, all snapshot files are saved using UTF-8 encoding. If you have existing snapshots created with an older version that might have used a different encoding, they could lead to comparison errors after upgrading.

fix

It is recommended to regenerate all existing snapshots after upgrading to version 0.5.0 or later to ensure consistent UTF-8 encoding.

affects: >=0.5.0

gotchaAttempting to snapshot test certain unsupported values, such as strings containing the carriage return character ('\r'), will raise a `ValueError`. This behavior was introduced to clarify unsupported inputs.

fix

Modify the data to remove unsupported characters or types before passing it to `snapshot.assert_match`, or handle such cases explicitly in your test logic.

affects: >=0.6.3

gotchaIn versions prior to 0.8.1, `snapshot.assert_match` might not correctly raise exceptions when running pytest with both `--assert=plain` and without `--snapshot-update`. This could mask actual failures.

fix

Upgrade to version 0.8.1 or newer to ensure robust exception handling. If unable to upgrade, avoid using `--assert=plain` in conjunction with `pytest-snapshot` without `--snapshot-update`.

affects: <0.8.1

Upgrade

Version history

0.9.0latest on PyPI · released Apr 23, 2022

Audit

Dependencies

No dependency data recorded yet.

Agent activity

10 hits · last 30 days

node

Resources

githubhttps://github.com/joseph-roitman/pytest-snapshot ↗

packagehttps://pypi.org/project/pytest-snapshot/ ↗